Objective paper · 44 questions · partial

JAMB 2004 · UME

Topics include Number bases, Number foundations & fractions, Commercial arithmetic, Surds, Logarithms, Sets & Venn diagrams.

Our copy of this paper is missing questions 6, 12, 31, 39, 41, 49.

Sit this paper

Answer every question in order, timed if you like (suggested 30 min). You're marked when you hand in, then you see where to focus and the working for each question.

Or read it here: every question below has a worked solution.

Question 1

Find xx and yy respectively in the subtraction below, carried out in base 5.

4243−13x4y344\begin{array}{rcccc} & 4 & 2 & 4 & 3 \\ - & 1 & 3 & x & 4 \\ \hline & y & 3 & 4 & 4 \end{array}

Worked solution (try it first)
  1. Units: 3<43 < 4, so borrow 5: 8−4=48 - 4 = 4.
  2. Fives: 4−1=34 - 1 = 3 is less than xx, so borrow again: 8−x=48 - x = 4, giving x=4x = 4.
  3. 25s: 2−1=1<32 - 1 = 1 < 3, so borrow: 6−3=36 - 3 = 3. 125s: 4−1−1=24 - 1 - 1 = 2, so y=2y = 2.
  4. So x=4x = 4 and y=2y = 2, option C.

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Question 2

Find pp if 4516−p7=3056451_6 - p_7 = 305_6.

Worked solution (try it first)
  1. Change to base ten: 4516=144+30+1=175451_6 = 144 + 30 + 1 = 175 and 3056=108+5=113305_6 = 108 + 5 = 113.
  2. So p=175−113=62p = 175 - 113 = 62 in base ten.
  3. Write 62 in base seven: 62=1×49+1×7+662 = 1 \times 49 + 1 \times 7 + 6, so p=1167p = 116_7, option C.

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Question 3

Simplify 110×23+1412÷35−14\dfrac{\frac1{10} \times \frac23 + \frac14}{\frac12 \div \frac35 - \frac14}.

Worked solution (try it first)
  1. Top: multiply first, 110×23=115\frac{1}{10} \times \frac23 = \frac{1}{15}.
  2. Then 115+14=460+1560\frac{1}{15} + \frac14 = \frac{4}{60} + \frac{15}{60}
    =1960= \frac{19}{60}.
  3. Bottom: divide first by flipping, 12÷35=12×53\frac12 \div \frac35 = \frac12 \times \frac53
    =56= \frac56.
  4. Then 56−14=1012−312\frac56 - \frac14 = \frac{10}{12} - \frac{3}{12}
    =712= \frac{7}{12}.
  5. Top divided by bottom: 1960×127=1935\frac{19}{60} \times \frac{12}{7} = \frac{19}{35}, option D.

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Question 4

A farmer planted 5000 grains of maize and harvested 5000 cobs, each bearing 500 grains. What is the ratio of the number of grains sowed to the number harvested?

Worked solution (try it first)
  1. Grains harvested: 5000 cobs with 500 grains each is 5000×500=2 500 0005000 \times 500 = 2\,500\,000 grains.
  2. Grains sowed to grains harvested: 5000:2 500 0005000 : 2\,500\,000.
  3. Divide both by 5000: 1:5001 : 500, option A.

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Question 5

Three teachers shared a packet of chalk. The first teacher got 25\frac25 of the chalk and the second teacher received 215\frac2{15} of the remainder. What fraction did the third teacher receive?

Worked solution (try it first)
  1. After the first teacher takes 25\frac25, the remainder is 35\frac35 of the chalk.
  2. The second gets 215\frac{2}{15} of the remainder: 215×35=675\frac{2}{15} \times \frac35 = \frac{6}{75}
    =225= \frac{2}{25}.
  3. The third gets the rest: 1−1025−225=13251 - \frac{10}{25} - \frac{2}{25} = \frac{13}{25}, option C.

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Question 7

Simplify 13+2\dfrac{1}{\sqrt3 + 2} in the form a+b3a + b\sqrt3.

Worked solution (try it first)
  1. Multiply the top and bottom by the conjugate of the bottom, 2−32 - \sqrt3.
  2. Bottom: (2+3)(2−3)=4−3(2 + \sqrt3)(2 - \sqrt3) = 4 - 3, which is 1.
  3. So the value is 2−32 - \sqrt3, option C.

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Question 8

If 6log⁡x2−3log⁡x3=3log⁡50.26\log_x 2 - 3\log_x 3 = 3\log_5 0.2, find xx.

Worked solution (try it first)
  1. Right side: 0.2=5−10.2 = 5^{-1}, so 3log⁡50.2=3(−1)=−33\log_5 0.2 = 3(-1) = -3.
  2. Left side: 6log⁡x2=log⁡x646\log_x 2 = \log_x 64 and 3log⁡x3=log⁡x273\log_x 3 = \log_x 27, so the left side is log⁡x6427\log_x \frac{64}{27}.
  3. Change to index form: x−3=6427x^{-3} = \frac{64}{27}, so x3=2764x^3 = \frac{27}{64}.
  4. Take cube roots: x=34x = \frac34, option B.

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Question 9

The shaded region in the Venn diagram is

PQR
Worked solution (try it first)
  1. The shaded region lies inside both QQ and RR, which gives Q∩RQ \cap R.
  2. It lies outside PP, which gives PcP^c.
  3. Together: Pc∩(Q∩R)P^c \cap (Q \cap R), option A.

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Question 10

In a class of 40 students, each student offers at least one of Physics and Chemistry. If the number that offer Physics is three times the number that offer both, and the number that offer Chemistry is twice the number that offer Physics, find the number of students that offer Physics only.

Worked solution (try it first)
  1. Let bb offer both.
  2. Then 3b3b offer Physics and 2×3b=6b2 \times 3b = 6b offer Chemistry.
  3. Everyone offers at least one, so 3b+6b−b=403b + 6b - b = 40, which gives 8b=408b = 40 and b=5b = 5.
  4. Physics has 3×5=153 \times 5 = 15 students, so Physics only is 15−5=1015 - 5 = 10, option C.

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Question 11

Find the values of xx where the curve y=x3+2x2−5x−6y = x^3 + 2x^2 - 5x - 6 crosses the xx-axis.

Worked solution (try it first)
  1. The curve crosses the xx-axis where y=0y = 0.
  2. Try small numbers: f(2)=8+8−10−6=0f(2) = 8 + 8 - 10 - 6 = 0, so x−2x - 2 is a factor.
  3. Divide out x−2x - 2: x3+2x2−5x−6=(x−2)(x2+4x+3)x^3 + 2x^2 - 5x - 6 = (x - 2)(x^2 + 4x + 3).
  4. Factorise: x2+4x+3=(x+1)(x+3)x^2 + 4x + 3 = (x + 1)(x + 3), so the roots are 2,−12, -1 and −3-3, option C.

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Question 13

Factorize completely ac−2bc−a2+4b2ac - 2bc - a^2 + 4b^2.

Worked solution (try it first)
  1. Group the first two and last two terms: c(a−2b)−(a2−4b2)c(a - 2b) - (a^2 - 4b^2).
  2. Factorise the difference of two squares: a2−4b2=(a−2b)(a+2b)a^2 - 4b^2 = (a - 2b)(a + 2b).
  3. Take out the common bracket: (a−2b)[c−(a+2b)]=(a−2b)(c−a−2b)(a - 2b)[c - (a + 2b)] = (a - 2b)(c - a - 2b), option B.

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Question 14

yy is inversely proportional to xx and y=4y = 4 when x=12x = \frac12. Find xx when y=10y = 10.

Worked solution (try it first)
  1. Inverse proportion means xyxy is constant: k=12×4=2k = \frac12 \times 4 = 2.
  2. When y=10y = 10: x=210=15x = \dfrac{2}{10} = \dfrac15, option B.

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Question 15

The length LL of a simple pendulum varies directly as the square of its period TT. If a pendulum with period 4 s is 64 cm long, find the length of a pendulum whose period is 9 s.

Worked solution (try it first)
  1. L=kT2L = kT^2.
  2. Put in T=4T = 4, L=64L = 64: 64=16k64 = 16k, so k=4k = 4.
  3. When T=9T = 9: L=4×81=324L = 4 \times 81 = 324 cm, option D.

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Question 16

The shaded area in the diagram is represented by

xy(0, 6)(2, 0)(0, 0)
The vertical scale is half the horizontal scale.
Worked solution (try it first)
  1. The line through (0,6)(0, 6) and (2,0)(2, 0) has gradient 0−62−0=−3\frac{0 - 6}{2 - 0} = -3 and yy-intercept 6, so y=−3x+6y = -3x + 6, that is y+3x=6y + 3x = 6.
  2. The shaded side contains the origin, where y+3x=0<6y + 3x = 0 < 6.
  3. So the region is y+3x<6y + 3x < 6, option A.

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Question 17

What are the integral values of xx which satisfy the inequality −1<3−2x≤5-1 < 3 - 2x \le 5?

Worked solution (try it first)
  1. Subtract 3 from all three parts: −4<−2x≤2-4 < -2x \le 2.
  2. Divide all three parts by −2-2 and reverse both signs: 2>x≥−12 > x \ge -1.
  3. Read from the left: −1≤x<2-1 \le x < 2.
  4. So −1-1 is included and 2 is not: the integers are −1-1, 00 and 11, option C.

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Question 18

The nnth terms of two sequences are Qn=3⋅2n−2Q_n = 3 \cdot 2^{n - 2} and Um=3⋅22m−3U_m = 3 \cdot 2^{2m - 3}. Find the product of Q2Q_2 and U2U_2.

Worked solution (try it first)
  1. Put n=2n = 2 into QnQ_n: Q2=3×20=3Q_2 = 3 \times 2^0 = 3.
  2. Put m=2m = 2 into UmU_m: the power is 2×2−3=12 \times 2 - 3 = 1, so U2=3×2=6U_2 = 3 \times 2 = 6.
  3. So Q2×U2=3×6=18Q_2 \times U_2 = 3 \times 6 = 18, option D.

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Question 19

Given that the first and fourth terms of a G.P. are 6 and 162 respectively, find the sum of the first three terms of the progression.

Worked solution (try it first)
  1. The 4th term of a G.P. is ar3ar^3, so 6r3=1626r^3 = 162 and r3=27r^3 = 27.
  2. Take the cube root: r=3r = 3.
  3. The first three terms are 6, 18 and 54, and their sum is 78, option D.

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Question 20

Find the sum to infinity of the series 12,16,118,…\frac12, \frac16, \frac1{18}, \dots

Worked solution (try it first)
  1. This is a G.P. with a=12a = \frac12 and r=16÷12=13r = \frac16 \div \frac12 = \frac13.
  2. Since rr is between −1-1 and 1, S∞=a1−rS_\infty = \dfrac{a}{1 - r}, and 1−13=231 - \frac13 = \frac23.
  3. Dividing by 23\frac23 means multiplying by 32\frac32: S∞=12×32S_\infty = \frac12 \times \frac32
    =34= \frac34, option B.

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Question 21

If the operation ∗* on the set of integers is defined by p∗q=pqp * q = \sqrt{pq}, find the value of 4∗(8∗32)4 * (8 * 32).

Worked solution (try it first)
  1. Work out the bracket first: 8∗32=8×328 * 32 = \sqrt{8 \times 32}
    =256= \sqrt{256}
    =16= 16.
  2. Then 4∗16=4×164 * 16 = \sqrt{4 \times 16}
    =64= \sqrt{64}
    =8= 8, option B.

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Question 22

The inverse of the matrix (2111)\begin{pmatrix} 2 & 1 \\ 1 & 1 \end{pmatrix} is

Worked solution (try it first)
  1. The determinant is 2×1−1×1=12 \times 1 - 1 \times 1 = 1.
  2. Swap the two diagonal entries (2 and 1) and change the signs of the other two: (1−1−12)\begin{pmatrix} 1 & -1 \\ -1 & 2 \end{pmatrix}.
  3. Divide by the determinant, 1, which changes nothing.
  4. The inverse is option D.

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Question 23

If P=(10−1345−101)P = \begin{pmatrix} 1 & 0 & -1 \\ 3 & 4 & 5 \\ -1 & 0 & 1 \end{pmatrix}, then ∣P∣|P| is

Worked solution (try it first)
  1. Expand along the first row, with signs +  −  ++ \; - \; +.
  2. The first term is 1×(4×1−5×0)=41 \times (4 \times 1 - 5 \times 0) = 4.
  3. The second term is 0, because the entry is 0.
  4. The third term is −1×(3×0−4×(−1))=−1×4-1 \times (3 \times 0 - 4 \times (-1)) = -1 \times 4
    =−4= -4.
  5. So ∣P∣=4−4=0|P| = 4 - 4 = 0, option B.
  6. (Row 3 is row 1 times −1-1, and that always makes the determinant 0.)

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Question 24

The sum of the interior angles of a pentagon is 6x+6y6x + 6y. Find yy in terms of xx.

Worked solution (try it first)
  1. The interior angles of a pentagon add up to (5−2)×180∘=540∘(5 - 2) \times 180^\circ = 540^\circ, so 6x+6y=5406x + 6y = 540.
  2. Divide by 6: x+y=90x + y = 90.
  3. Subtract xx: y=90−xy = 90 - x, option B.

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Question 25

PQRSTVPQRSTV is a regular polygon of side 7 cm inscribed in a circle. Find the circumference of the circle PQRSTVPQRSTV. [π=227]\left[\pi = \frac{22}{7}\right]

Worked solution (try it first)
  1. PQRSTVPQRSTV has six sides, so it is a regular hexagon.
  2. Joining the centre to each vertex makes six equilateral triangles, so the radius equals the side: r=7r = 7 cm.
  3. Circumference =2πr=2×227×7= 2\pi r = 2 \times \frac{22}{7} \times 7.
  4. So the circumference is 44 cm, option C.

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Question 26

PP, RR and SS lie on a circle centre OO as shown, while QQ lies outside the circle. Find ∠PSO\angle PSO.

20°35°OPQRS
Worked solution (try it first)
  1. QQ, RR and SS are in a straight line, so ∠PRS\angle PRS is the exterior angle of triangle PQRPQR: ∠PRS=20∘+35∘\angle PRS = 20^\circ + 35^\circ
    =55∘= 55^\circ.
  2. The angle at the centre is twice the angle at the circumference on the same arc PSPS: ∠POS=2×55∘\angle POS = 2 \times 55^\circ
    =110∘= 110^\circ.
  3. OP=OSOP = OS (radii), so triangle POSPOS is isosceles and its base angles are equal.
  4. So ∠PSO=180∘−110∘2\angle PSO = \frac{180^\circ - 110^\circ}{2}
    =35∘= 35^\circ, option A.

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Question 27

In the diagram, PQ=4PQ = 4 cm and TS=6TS = 6 cm; PQTUPQTU and PQRSPQRS are parallelograms. If the area of parallelogram PQTUPQTU is 32 cm232\text{ cm}^2, find the area of the trapezium PQRUPQRU.

4 cm6 cmUTSRPQ
Worked solution (try it first)
  1. Area of parallelogram PQTUPQTU is base × height, so the height is 32÷4=832 \div 4 = 8 cm.
  2. Both parallelograms give UT=PQ=4UT = PQ = 4 cm and SR=PQ=4SR = PQ = 4 cm.
  3. So UR=4+6+4=14UR = 4 + 6 + 4 = 14 cm.
  4. Trapezium PQRUPQRU: 12(4+14)×8=72 cm2\frac12(4 + 14) \times 8 = 72\text{ cm}^2, option D.

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Question 28

An arc of a circle of length 22 cm subtends an angle of 3x∘3x^\circ at the centre of the circle. Find the value of xx if the diameter of the circle is 14 cm. [π=227]\left[\pi = \frac{22}{7}\right]

Worked solution (try it first)
  1. The circumference is 227×14=44\frac{22}{7} \times 14 = 44 cm.
  2. An arc of 22 cm is half of it.
  3. So the arc subtends half of 360∘360^\circ: 3x=1803x = 180.
  4. So x=60∘x = 60^\circ, option B.

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Question 29

Determine the locus of a point inside a square PQRSPQRS which is equidistant from PQPQ and QRQR.

Worked solution (try it first)
  1. PQPQ and QRQR meet at the corner QQ.
  2. Points equidistant from two lines that meet lie on the bisector of the angle between them, here ∠PQR\angle PQR.
  3. In a square, the diagonal from QQ bisects the right angle at QQ.
  4. That diagonal is QSQS, option B.

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Question 30

The locus of a point which is 5 cm from the line LMLM is a

Worked solution (try it first)
  1. Points 5 cm from a line can be on either side of it, so there are two lines, each parallel to LMLM and 5 cm from it.
  2. So the locus is a pair of lines on opposite sides of LMLM, each 5 cm from it, option A.

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Question 32

Find the midpoint of the line joining P(−3,5)P(-3, 5) and Q(5,−3)Q(5, -3).

Worked solution (try it first)
  1. The midpoint is the average of the ends: add the coordinates and halve.
  2. xx: −3+52=1\frac{-3 + 5}{2} = 1.
  3. yy: 5+(−3)2=1\frac{5 + (-3)}{2} = 1.
  4. So the midpoint is (1,1)(1, 1), option D.

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Question 33

In the triangle shown, the base angles are 45∘45^\circ and 60∘60^\circ, the side opposite the 60∘60^\circ angle is 15 cm and the side opposite the 45∘45^\circ angle is xx. Find xx.

15 cmx45°60°
Worked solution (try it first)
  1. Sine rule: xx faces the 45∘45^\circ angle and 15 cm faces the 60∘60^\circ angle, so xsin⁡45∘=15sin⁡60∘\dfrac{x}{\sin45^\circ} = \dfrac{15}{\sin60^\circ}.
  2. So x=15×2232x = \dfrac{15 \times \frac{\sqrt2}{2}}{\frac{\sqrt3}{2}}
    =1523= \dfrac{15\sqrt2}{\sqrt3}.
  3. Rationalise: multiply top and bottom by 3\sqrt3 to get 1563=56\dfrac{15\sqrt6}{3} = 5\sqrt6 cm, option C.

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Question 34

The shadow of a pole 535\sqrt3 m high is 5 m. Find the angle of elevation of the sun.

Worked solution (try it first)
  1. The pole is opposite the angle of elevation and the shadow is adjacent, so tan⁡θ=535=3\tan\theta = \frac{5\sqrt3}{5} = \sqrt3.
  2. tan⁡60∘=3\tan60^\circ = \sqrt3, so θ=60∘\theta = 60^\circ, option C.

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Question 35

Find the derivative of (2+3x)(1−x)(2 + 3x)(1 - x) with respect to xx.

Worked solution (try it first)
  1. Expand first: (2+3x)(1−x)=2−2x+3x−3x2(2 + 3x)(1 - x) = 2 - 2x + 3x - 3x^2
    =2+x−3x2= 2 + x - 3x^2.
  2. Differentiate term by term: 1−6x1 - 6x, option B.

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Question 36

Find the derivative of the function y=2x2(2x−1)y = 2x^2(2x - 1) at the point x=−1x = -1.

Worked solution (try it first)
  1. Expand: y=4x3−2x2y = 4x^3 - 2x^2.
  2. Differentiate: dydx=12x2−4x\frac{dy}{dx} = 12x^2 - 4x.
  3. At x=−1x = -1: 12(1)−4(−1)=12+4=1612(1) - 4(-1) = 12 + 4 = 16, option C.

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Question 37

If y=3cos⁡x3y = 3\cos\frac x3, find dydx\frac{dy}{dx} when x=3π2x = \frac{3\pi}{2}.

Worked solution (try it first)
  1. Chain rule: cos⁡x3\cos\frac x3 differentiates to −13sin⁡x3-\frac13\sin\frac x3, so dydx=3×(−13)sin⁡x3\frac{dy}{dx} = 3 \times \left(-\frac13\right)\sin\frac x3
    =−sin⁡x3= -\sin\frac x3.
  2. At x=3π2x = \frac{3\pi}{2}, x3=π2\frac x3 = \frac\pi2 and sin⁡π2=1\sin\frac\pi2 = 1.
  3. So dydx=−1\frac{dy}{dx} = -1, option C.

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Question 38

What is the rate of change of the volume VV of a hemisphere with respect to its radius rr when r=2r = 2?

Worked solution (try it first)
  1. A hemisphere is half a sphere, so V=12×43πr3V = \frac12 \times \frac43\pi r^3
    =23πr3= \frac23\pi r^3.
  2. Differentiate: dVdr=2πr2\frac{dV}{dr} = 2\pi r^2.
  3. At r=2r = 2: 2π×4=8π2\pi \times 4 = 8\pi, option C.

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Question 40

The pie chart shows the distribution of the crops harvested from a farmland in a year. If 3000 tonnes of millet is harvested, what amount of beans is harvested?

Others 60°BeansMillet 150°Maize
Worked solution (try it first)
  1. Maize is marked with a right angle, so it is 90∘90^\circ.
  2. Beans is the rest: 360∘−60∘−90∘−150∘=60∘360^\circ - 60^\circ - 90^\circ - 150^\circ = 60^\circ.
  3. Millet's 150∘150^\circ stands for 3000 tonnes, so 1∘1^\circ stands for 3000÷150=203000 \div 150 = 20 tonnes.
  4. Beans: 60×20=120060 \times 20 = 1200 tonnes, option D.

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Question 42

The graph shows the cumulative frequency curve of the distribution of marks in a class test. What percentage of the students scored more than 20 marks?

5101520259141924293439Cumulative frequencyMarks
Worked solution (try it first)
  1. The curve ends at 25, so there are 25 students.
  2. Read the curve at 20 marks: the cumulative frequency is 18, so 18 students scored 20 or less.
  3. So 25−18=725 - 18 = 7 students scored more than 20.
  4. As a percentage: 725×100=28%\frac{7}{25} \times 100 = 28\%, option B.

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Question 43

The mean age of a group of students is 15 years. When the age of a teacher, 45 years old, is added, the mean becomes 18 years. Find the number of students in the group.

Worked solution (try it first)
  1. Let there be nn students.
  2. Their total age is 15n15n.
  3. With the teacher it is 15n+4515n + 45 for n+1n + 1 people.
  4. The new mean is 18, so 15n+45=18(n+1)=18n+1815n + 45 = 18(n + 1) = 18n + 18.
  5. Collect terms: 27=3n27 = 3n, so n=9n = 9, option B.

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Question 44

The weights of 10 pupils in a class are 15 kg, 16 kg, 17 kg, 18 kg, 16 kg, 17 kg, 17 kg, 17 kg, 18 kg and 16 kg. What is the range of this distribution?

Worked solution (try it first)
  1. The heaviest pupil is 18 kg and the lightest is 15 kg.
  2. The range is 18−15=318 - 15 = 3 kg, option C.

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Question 45

Find the mean deviation of 1, 2, 3 and 4.

Worked solution (try it first)
  1. The mean of 1, 2, 3, 4 is 2.5.
  2. The distances from 2.5 are 1.5, 0.5, 0.5 and 1.5, which add up to 4.
  3. The mean deviation is 44=1.0\frac44 = 1.0, option A.

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Question 46

In how many ways can 2 students be selected from a group of 5 students in a debating competition?

Worked solution (try it first)
  1. The two students form a pair, so their order doesn't matter: use 5C2^5C_2.
  2. 5C2=5×42×1^5C_2 = \dfrac{5 \times 4}{2 \times 1}
    =10= 10 ways, option A.

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Question 47

A committee of six is to be formed by a state governor from nine state commissioners and three members of the state house of assembly. In how many ways can the committee be chosen so as to include one member of the house of assembly?

Worked solution (try it first)
  1. Choose the one assembly member from three: 3C1=3^3C_1 = 3 ways.
  2. The other 5 places go to commissioners, 5 from 9: 9C5=126^9C_5 = 126 ways.
  3. Multiply: 3×126=3783 \times 126 = 378 ways, option D.

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Question 48

Some white balls were put in a basket containing twelve red balls and sixteen black balls. If the probability of picking a white ball from the basket is 37\frac37, how many white balls were introduced?

Worked solution (try it first)
  1. Let ww white balls be added.
  2. The total becomes 12+16+w=28+w12 + 16 + w = 28 + w.
  3. So w28+w=37\frac{w}{28 + w} = \frac37.
  4. Cross-multiply: 7w=84+3w7w = 84 + 3w.
  5. Take 3w3w from both sides: 4w=844w = 84, so w=21w = 21, option C.

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Question 50

A container has 30 gold medals, 22 silver medals and 18 bronze medals. If one medal is selected at random, what is the probability that it is not a gold medal?

Worked solution (try it first)
  1. There are 30+22+18=7030 + 22 + 18 = 70 medals.
  2. Not gold means silver or bronze: 22+18=4022 + 18 = 40 medals.
  3. So the probability is 4070=47\frac{40}{70} = \frac47, option A.

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