Question

P and q are two points 100 km apart. A starts from p towards q at 10km/hr. B starts running from q at exactly same time and in the same direction as that of a at 20km/hr. After an hour, b turns back and changes his speed to 10km/hr. After another hour, b again turns back and changes his speed to 20km/ht. He keeps on changing his speed and direction in this same manner till the time he meets
a. After how much time will a and be meet for the first time?

Answer 1

Answer:

After 20 hrs they will meet first

Step-by-step explanation:

B starts running from q at exactly same time and in the same direction as that of a at 20km/hr

=> Distance covered by B  in 1 hr = 20 km

then Distance covered by B in next 1 hr = - 10 km

Distance covered by B in 2 hrs = 10 km

This keep on Repeating

A starts from p towards q at 10km/hr.

Distance covered in every hour = 10 km

Let say after 2t hrs they meet

=> Distance covered by A = 20t

Distance covered by B = 10t

20t  = 100 + 10t    ( 100 is  distance between P & Q)

=> 10t = 100

=> t = 10

=> After 2t = 20 hrs

After 20 hrs they will meet first