Question

Places A and B are 100 km apart on a highway. One car starts from A and another from B at the same time. If the cars travel in the same direction at different speeds, they meet in 5 hours. If they travel towards each other, they meet in 1 hour. What are the speeds of the two cars? ( Solve the question by cross multiplication method )​

Answer 1

Answer:

Let the speed of car at A be x kmph

and the speed of car at B be y kmph

when the car travel in same direction Relative Speed is x−y

Dist=100km

t=5 hours

∴  Dist =S×T

100=(x−y)5

x−y=20⟶(I)

when car travel in opposite direction Relative Speed is x+y

Dist=100km

t=1 hours

Dist=ST

100=(x+y)1

x+y=100⟶(II)

Solving (I) & (II)

x−y=20

x+y=100

   2x=120

x=60km/h

y=40km/h

Speed of the car at A =60 km/h

Speed of the car at B=40 km/h

The difference of speeds is 60−40=20

Answer 2

Answer:

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Let the speed of car at A be x km/h

and the speed of car at B be y km/h

As per the question,

5x - 5y = 100

x - y = 20 ... (1)

and x + y = 100 ... (2)

Solving (1) and (2), we get,

x = 60 and y = 40

Speed of the car at A = 60 km/h

Speed of the car at B = 40 km/h