Number · SS1–SS2

Approximation & error

Rounding sensibly, significant figures and how big an error a rounded value can hide.

Before this: Number foundations & fractions

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1Approximation and errorRounding to decimal places and significant figures, rounding only at the end of a calculation, and percentage error.Done12 min

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Answer approximation & error questions one at a time. You'll know straight away whether you're right, with hints and the working step by step.

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Past questions (41)

From 1983–2024: 10 WAEC, 7 NECO, 24 JAMB. Theory questions first, then objective, newest first.

Theory (1)

NECO 2022 · Paper 2 · Q10A composite solid consists of a cone on top of a cylinder. The cone is 8 cm high and its slant height is 10 cm. If the solid is 18 cm high, calculate …

Objective (40)

NECO 2024 · Paper 1 · Q1Express 384.126 to the nearest hundred.
NECO 2024 · Paper 1 · Q7A wire of length $25\text{ cm}$ was measured by a student to be $24.4\text{ cm}$ . Find the percentage error.
WAEC 2024 · Paper 1 · Q10A trader gave a change of ₦540.00 instead of ₦570.00 to a customer. Calculate the percentage error.
NECO 2023 · Paper 1 · Q11In a Chemistry class, a student recorded $21.23\text{ cm}^3$ for a titre value of $21.32\text{ cm}^3$ . Find the percentage error, correct to …
WAEC 2023 · Paper 1 · Q1Evaluate, correct to three decimal places, $\dfrac{4.314 \times 0.000056}{0.0067}$ .
WAEC 2023 · Paper 1 · Q20A notebook of length $15\text{ cm}$ was measured to be $16.8\text{ cm}$ . Calculate, correct to two decimal places, the percentage error in the …
WAEC 2023 · Paper 1 · Q36A student measured the height of a pole as $5.98\text{ m}$ , which is less than the actual height. If the percentage error is $5\%$ , find, correct …
NECO 2022 · Paper 1 · Q1Express 0.0030752 to three significant figures.
NECO 2022 · Paper 1 · Q10A square of side 10 cm is measured by a student as 9.9 cm. If she uses her measurement to calculate the area of the square, calculate the percentage …
NECO 2022 · Paper 1 · Q7Approximate 8.5326 to the nearest hundredth.
WAEC 2022 · Paper 1 · Q1Evaluate, correct to four significant figures, $573.06 \times 184.25$ .
WAEC 2022 · Paper 1 · Q12The length of a piece of stick is $1.75\text{ m}$ . A boy measured it as $1.80\text{ m}$ . Find the percentage error.
WAEC 2021 · Paper 1 · Q1Correct 0.007985 to three significant figures.
WAEC 2020 · Paper 1 · Q1Evaluate and correct to two decimal places: $75.0785 - 34.624 + 9.83$ .
WAEC 2019 · Paper 1 · Q1Express, correct to three significant figures, 0.003597.
WAEC 2019 · Paper 1 · Q4Simplify, correct to three significant figures, $(27.63)^2 - (12.37)^2$ .
JAMB 2018 · UTME · Q16Correct each of 59.81798 and 0.0746829 to three significant figures and multiply them, giving your answer to three significant figures.
JAMB 2017 · UTME (set 2) · Q22If a rod $10\text{ cm}$ in length was measured as $10.5\text{ cm}$ , calculate the percentage error.
JAMB 2013 · UTME · Q4Evaluate $\dfrac{1.25 \times 0.025}{0.05}$ , correct to 1 decimal place.
JAMB 2012 · UTME · Q4Evaluate $\frac{21}{9}$ to 3 significant figures.
JAMB 2010 · UTME · Q4A student measures a piece of rope and found that it was $1.26\text{ m}$ long. If the actual length of the rope was $1.25\text{ m}$ , what was …
JAMB 2001 · UME · Q3Evaluate $21.05347 - 1.6324 \times 0.43$ , to 3 decimal places.
JAMB 2001 · UME · Q4Evaluate $\dfrac{(0.14)^2 \times 0.275}{7 \times 0.02}$ correct to 3 decimal places.
JAMB 2000 · UME · Q5Evaluate $\dfrac{(2.813 \times 10^{-3}) \times 1.063}{5.637 \times 10^{-2}}$ , reducing each number to two significant figures and leaving your …
JAMB 1997 · UME · Q2Evaluate $64.764^2 - 35.236^2$ correct to 3 significant figures.
JAMB 1995 · UME · Q2Write 3.1415926 correct to 5 decimal places.
JAMB 1995 · UME · Q3The length of a notebook, 15 cm, was measured as 16.8 cm. Calculate the percentage error to 2 significant figures.
JAMB 1994 · UME · Q2Evaluate $(0.36 \times 5.4 \times 0.63) \div (4.2 \times 9.0 \times 2.4)$ , correct to 2 significant figures.
JAMB 1993 · UME · Q2Evaluate $\frac{3524}{0.05}$ correct to 3 significant figures.
JAMB 1992 · UME · Q2The radius of a circle is given as 5 cm subject to an error of 0.1 cm. What is the percentage error in the area of the circle?
JAMB 1991 · UME · Q3Find, correct to 3 decimal places, $\left(\dfrac{1}{0.05} \div \dfrac{1}{5.005}\right) - (0.05 \times 2.05)$ .
JAMB 1991 · UME · Q4Express $\frac{62}{3}$ as a decimal correct to 3 significant figures.
JAMB 1990 · UME · Q3Correct $241.34 \times (3 \times 10^{-3})^2$ to 4 significant figures.
JAMB 1989 · UME · Q6What is the difference between 0.007685 correct to three significant figures and 0.007685 correct to four decimal places?
JAMB 1988 · UME · Q4Find, correct to one decimal place, $0.24633 \div 0.0306$ .
JAMB 1987 · UME · Q13Instead of writing $\frac{35}{6}$ as a decimal correct to 3 significant figures, a student wrote it correct to 3 decimal places. Find his error …
JAMB 1987 · UME · Q4Reduce each number to two significant figures and then evaluate $\dfrac{0.02174 \times 1.2047}{0.023789}$ .
JAMB 1985 · UME · Q5Find, correct to two decimal places, $100 + \frac{1}{100} + \frac{3}{1000} + \frac{27}{10000}$ .
JAMB 1983 · UME · Q30Correct each of the numbers 59.81789 and 0.0746829 to three significant figures and multiply them, giving your answer to three significant figures.
JAMB 1983 · UME · Q31A rod of length 250 cm is measured as 255 cm. What is the percentage error in the measurement?