Question

a train travel a diatance of 480 km at a uniform speed.if the speed had been 8km/h less then it would have taken 3hours more to cover the same distance.find speed of train

Answer 1

Let..,
Speed be v
Time be T

Speed = Distance / Time
Distance = Speed * Time
480 = vT ——(1)

According to question
480 = (v - 8)*(T + 3)
From equation (1) 480 = vT
vT = (v - 8)(T + 3)
vT = v(T + 3) - 8(T + 3))
vT = vT + 3v - 8T - 24
3v = 8T + 24
From equation (1) T = 480/v
3v = 8*480/v + 24
3v - 3840/v = 24
3v^2 - 3840 = 24v
3v^2 - 24v - 3840 = 0
v^2 - 8v - 1280 = 0
Solve this polynomial equation
We will get v = 40km/h and v = -32km/h
Speed can’t be be negative.

Therefore speed of train is 40km/h