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/hr and 48 km/hr respectively After 15 seconds, the distance between them will be

A) 400m             

B)          150m

C) 300m             

D)          250m

Correct Answer: D

Solution :

    Distance travelled by the 1st car in 15 seconds \[=OA=\left( 36\times \frac{5}{18} \right)\,\times 15\,m=150m\] Distance travelled by the 2nd car in 15 seconds \[=OB=\left( 48\times \frac{5}{18} \right)\,\times 15\,m=200\,m\] \[\therefore \] Distance between them after 15 seconds \[=AB=\sqrt{O{{A}^{2}}+O{{B}^{2}}}\,=\sqrt{{{150}^{2}}+{{200}^{2}}}\] \[=\sqrt{22500+40000}\] \[=\sqrt{62500}=\,250\,m\].