Discussion Forum



1)

Two persons ride towards each other from 2 places 55 km apart, one riding at 12 km/hr and the other 10 km/h. When will they be first 11 km apart .If they continue riding, after how much time will they be again 11 km apart?


A) 2 h,1 h

B) 3 h, 2h

C) 1 h, 2 h

D) 4 h, 2 h

E) None of these

Answer:

Option A

Explanation:

Let A and B be two places 55 km apart.

Let M and N be the positions of the two persons ,when they first 11 km apart.

Let them be so ,x hours after thei simultaneous start .

Then AM + MN +NB = 55

12x + 11 + 10x  = 55

22 x  = 44

X = 2 hrs

Now let P and Q be their respective  positions (PQ = 11 km)

Let them be in the position   y hrs after starting  from A and B

AP + BQ – PQ  = 55

12y + 10y -11 = 55

Y = 3

Now 3 - 2 = 1

1 Hour after their first 11 km apart position they will again be 11 km apart.