Question

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) 400 m 

(b) 150 m 

(c) 300 m 

(d) 250 m

Answer 1

(d) 250 m

Distance travelled by the 1st car in 15 seconds

= OA = \(\bigg(36\times\frac{5}{18}\bigg)\)x 15 m = 150 m

Distance travelled by the 2nd car in 15 seconds

= OB = \(\bigg(48\times\frac{5}{18}\bigg)\)x 15 m = 200 m

∴ Distance between them after 15 seconds

= AB = \(\sqrt{OA^2+OB^2} = \sqrt{150^2+200^2}\)

= \(\sqrt{22500+40000}\)

= \(\sqrt{62500}\) = 250 m.