Question

A car travels a distance of 840 km at a
uniform speed. If the speed of the car is
10 km/h more, then it takes 2 h less to cover
the same distance. The original speed of the
car was
(a) 45 km/h
(b) 50 km/h
(c) 60 km/h
(d) 75 km/h

Right answer and explanation will be marked brainliest

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Answer 1

Answer:

Let the original speed of car is x km \hr

Then time taken in moving 840 km=

x

840

hr

if speed is going 10 km \hr more =x+10

Then time taken in moving 840 km=

x+10

840

hr

∴

x

840

−

x+10

840

=2

⇒840(x+10)−840x=2x(x+10)

⇒2x

2

+20x−8400=0

⇒x

2

+70x+−60x−4200=0

⇒(x+70)(x−60)=0

⇒x=60orx=−70

If x=-70 is not true because speed not negetive

So speed is 60 km \ hr