Cars A and B start at the same time, from S and T towards T and s, respectively. After passing each other at point Y, they take 6 hours 40 minutes and 3 hours 45 minutes to reach T and S, respectively. If the speed of car A is 60 km/h, then how much time did Car A take to reach point Y?

Let the speed of car A be A and car B be B. Given that the speed of A is 60kmph. Let us assume that they both meet at Y after a time of t. A travels a distance of 400 in 6hr 40m. This distance is covered by B in t time.

400= $$B\cdot t$$. --->1

Again, the distance travelled by A in t time will be covered by B in 3hr 45m, which can be written as$$\ A\cdot t=B\cdot\ \frac{15}{4}$$ -->2

Substitute B =$$400/t$$ from eq 1. We know that A is 60.

$$60\cdot t=\left(\frac{400}{t}\right)\cdot\frac{15}{4}$$

$$t^2=25$$

t=5