question_answer

Two cars start at the same time from one point and move along two roads at right angles to each other. Their speeds are 36 km/h and 48 km/h respectively. After 15 s the distance between them will be

A)  400 m             

B)  150 m

C)  300 m             

D)  250 m

Correct Answer: D

Solution :

Let O be the starting point. The car running at 36 km/h is moving along OB and that at 48 km/h moving along 36 km/h OA. Also let they reach at B and A after 15 s respectively. \[\therefore \]      \[OA=48\times \frac{5}{18}\times 15=200\,m\] and       \[OB=36\times \frac{5}{18}\times 15=150\,m\] \[\therefore \] Required distance = AB             \[=\sqrt{{{(200)}^{2}}+{{(150)}^{2}}}\]             \[=\sqrt{40000+22500}=\sqrt{62500}=250\,m\]