Question

Points AandB are 90km apart from each other on a highway. A car starts from A and another from B at the same time. If they go in the same direction they meet in 9 hrs and if they go in opp direction they meet in 9/7 hrs. Find their speeds.

Answer 1

Answer:

Speed of car from A = 39.5 km/hr

Speed of car from B = 30.5 km/hr

Step-by-step explanation:

case I

two cars moving in same direction

let them meet at M after 9 hrs

•---------------•--------------------------------•

A B M

|<---90km--->|<--------- 9ykm ----------->|

|<-------------------- 9x km ----------------->|

Then, AM = 9x km

And, BM = 9y km

AM - BM = AB

9x - 9y = 90

9(x - y) = 90

x - y = 9 -----------(1)

Case II

let them meet at N after 9/7 hrs

•---------------------•--------------------------•

A N B

|<---9/7x km--->|<-------- 9/7y km----->|

|<-------------------- 90 km ----------------->|

then, AN = 9/7 x km

And, BN = 9/7 y km

AN + BN = AB

9/7 x + 9/7 y = 90

9/7 (x + y) = 90

x + y = 70 ------------(2)

adding (1) and (2), we get 2x = 79 ==⟩ x = 39.5

Putting x = 39.5 in (2), we get 39.5 + y = 70 ==⟩ y = 30.5

Speed of car from A = 39.5 km/hr

and Speed of car from B = 30.5 km/hr