19) B

Let faster driver be A
Let slower driver be B

Time of A = 1 minute 6 seconds = 66 seconds
Time of B = 1 minute 10 seconds = 70 seconds

Lapping means that the faster driver covered 1 more lap than the slower driver.
Let number of laps covered by B = n
Number of laps covered by A = n + 1

After lap 1, A would be 4 seconds ahead, after 2 laps, A would be 8 seconds ahead etc.

In order for A to lap B, we need the following equation to be satisfied:

66 x (n + 1) = 70 x (n)
66n + 66 = 70n
66 = 4n
n = 16.5 laps

So number of laps covered by A = n + 1 = 16.5 + 1 = 17.5

Time taken by A to cover 17.5 laps = 17.5 x 66 = 1155 seconds

1155 seconds = 19 minutes 15 seconds.

Leave a Reply