Question

X and Y two cars started running around the circular track of length 700 meters at speeds of 72 km/h and 36 km/h. In how much time they will meet for the first time at the starting point?

A. L.C.M of 72 and 36

B. L.C.M of 70 and 10

C. L.C.M of 70 and 35

D. 50

1. A
2. D
3. B and C
4. C

Answer 1

Correct Answer - Option 3 : B and C

Given:

Length of circular track = 700 meters

Speed of X = 72 km/hr

Speed of Y = 36 km/hr

Concept used:

To find the time taken to meet at starting point, take L.C.M of the time taken by persons

Calculation:

Speed of X in m/sec = 72 × (5/18) = 20 m/sec

Speed of Y in m/sec = 36 × (5/18) = 10 m/sec

⇒ Time taken by X to cover 700 meters = 700/20 = 35 sec

⇒ Time taken by Y to cover 700 meters = 700/10 = 70 sec

L.C.M of  70 & 35 = 70

B. L.C.M of 70 and 10

L.C.M of 70 and 10 = 70

B is correct

C. L.C.M of 70 and 35

L.C.M of 70 and 35 = 70

C is correct

∴ B and C are correct.