Question 855322
An athlete runs from A to B and back, at a speed of 10 kmph, 
while a second athlete simultaneously runs from B to A and back, at a speed of 15 kmph.
 If they cross each other for the first time 12 in min. after they start, then when will they meet each other for the second time.
:
It may help if we find the distance from A to B
Each will cover a portion of the total dist in 12 min
12 min = .2 hrs
d = .2(10) + .2(15)
d = 2 + 3
d = 5 km from A to B
:
to meet again, they have to travel 3 + 2 + 5 = 10 km, twice as far so in 24 min
:
------------------------------------------------------------------------------
Response to student question 
"how the distance between A & B will be 5 Km as we we calculate the distance for 12 min. "
:
We know that both runners ran for 12 min. Since we are using km/hr, we change 12 min to 12/60 = .2 hrs
We can find the distance each ran by multiplying the time times the speed
1st runner .2 * 10 = 2 km
2nd runner .2 * 15 = 3 km 
---------------------------
the total is the dist from A to B, hence 5 km