Number of laps car X made in 240 seconds
= 240s ÷ 60s/lap = 4 laps

Number of laps car Y made in 240 seconds
= 240s ÷ 80s/lap = 3 laps

So, every 240 seconds, Car X is 1 lap ahead of Car Y.

240 seconds = 4 minutes (240s ÷ 60s/min = 4 min)

So, for Car X to be 5 laps ahead,

Time needed = 4 minutes x 5 = 20 minutes

Thank you for your help and explanation :D

Another way for part b) :


Distance that Car X travels in 1 minute
= 2km

(1 lap in 60s means 1 lap per minute, and 1 lap is 2km long)

Distance Car Y travels in 1 minute
= 2km ÷ 80s x 60s
= 1.5km

Difference in distance travelled per minute = 2km - 1.5km = 0.5km

Now, 5 laps ahead also means = 5 x 2km = 10km ahead


Time needed for Car X to be 10km ahead
of Car Y = 10km ÷ 0.5km/min = 20 min

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