RRB NTPC Mains or Stage 2 Model Paper 5 with solutions

Question : 37 of 120

Marks: +1, -0

A car covers 420 km with a constant speed. If its speed were 10 km/h more it would have taken one hour less to cover the distance. Find the speed of the car.

60 km/h
55 km/h
50 km/h
48 km/h

Validate

Solution:

(a) Let the speed of car = S km /h.
Also, let previous time = t hr. Then,
420 = St … (i)
Also , 420 = (S + 10) (t – 1)
⇒

420 (S +10) [420/s -1]

[By (i)]

⇒s^2 + 10 S – 4200 = 0

⇒( S + 70) (S – 60) = 0

⇒ S = 60 km/h

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