WAEC 2018 · Paper 2 · Q3

(a)
The diagram shows an athletics track with two parallel sides and two semicircular ends. Each of the parallel sides is 60 metres long and the diameter of each semicircular end is 120 metres. Calculate the distance covered by an athlete who runs round the track two times. $\left[\text{Take }\pi = \frac{22}{7}\right]$
(b)
If the athlete spends 200 seconds for the race, calculate the speed in km/h.

Worked solution (try it first)

(a)

One lap is the two straights and the two semicircular ends.
The two semicircles make a whole circle of diameter 120 m: $\frac{22}{7} \times 120 \approx 377.14$ m.
One lap $= 2 \times 60 + 377.14 = 497.14$ m.
Two laps $= 2 \times 497.14 \approx 994.3$ m.

(b)

Speed $= \frac{994.29\text{ m}}{200\text{ s}}$
$\approx 4.97$ m/s.
To change m/s to km/h, multiply by 3.6 (3600 seconds in an hour, 1000 m in a km): $4.97 \times 3.6 \approx 17.9$ km/h.

Report a problem with this question