two places a and b are 120km apart from each other on highway. a car starts from a and another from b at the same time. if they move in thesame direction,they meet in 6 hours and if they move inopposite direction,they meet in 1 hour and 12 minute. find the speed of cars. please solve this question
Answers
speed of car at "a" be x kmph
speed of car at "b" be y kmph
dis covered by car at "a" in 6 hours = 6x
dis covered by car at "b" in 6 hours = 6y
Since they are travelling in same direction, sign shouble be negative
6x - 6y = 120
x - y = 20 ------------ (1)
1hr 12 min = 1 12/60 = 72/60 = 6/5 hr
Since they are travelling in opposite directions, sign should be positive.
(6/5)x + (6/5)y = 120
6x + 6y = 120×5
6x + 6y = 20×5
x + y = 100 ------------ (2)
Adding (1) and (2)
we get 2x = 120
x = 60
Putting x = 60 in (2)
we get y = 40
Therefore,speeds cars are 60 km/h & 40 km/h.
Answer:
Let the speed of the first car which
starts from A = x km /hr
Speed of the second car which starts
from B = y km / hr
We know that,
______________________
Time = distance / speed
______________________
Distance between two places A and
B are 80km
d = 80 km
i ) if the cars move in same direction
Relative speed of them = ( x + y )
km/hr
Time = 8hr
d = 80km
8 = 80 / ( x + y )
x + y = 80 / 8
x + y = 10 ------( 1 )
ii ) if two cars moving opposite
direction,
Relative speed = ( x - y ) km / hr
Time = 1 hr 20 minutes
= ( 1 + 20 / 60 ) hr
= ( 80/60)
= 4/3 hr
d = 80km
4/3 = 80 / ( x -y )
x -y = ( 80 × 3 ) / 4
x - y = 60-----( 2 )
Add ( 1 ) and ( 2 ) , we get
2x = 70
x = 35
Put x = 35 in ( 1 ) we get ,
y = 25
Therefore ,
Speed of the first car = x = 35km/hr
Speed of the second car = 25km /hr
I hope this helps you.
:)