Q20 of 29 Page 3

Places A and B are 80 km apart from each other on a highway. A car starts from A and other from B at the same time. If they move in the same direction, they meet in 8 hours and if they move in opposite directions, they meet in 1 hour and 20 minutes. Find the speeds of the cars.

To find: the speeds of the cars.


Explanation:


Let the speed of car from A be ‘a’ and of car from B be ‘b’.


Speed = distance/time


Relative speed of cars when moving in same direction = a + b


Relative speed of cars when moving in opposite direction = a – b


Given, places A and B are 80 km apart from each other on a highway. A car starts from A and other from B at the same time.




If they move in the same direction, they meet in 8 hours and



⇒ a–b = 10 …… (1)


if they move in opposite directions, they meet in 1 hour and 20 minutes.





⇒ a + b = 60


Adding (1) and (2)


⇒ a – b + a + b = 10 + 60


⇒ 2a = 70


⇒ a = 35 km/hr


Put the value of “a” in (1).


Thus, b = 35 – 10 = 25 km/hr


Hence, speed of two cars are 35km/h and 25 km/h.


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