Question

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

Answer 1

Let V km/hr = speed of train
Let it travel for T hrs time.
480 km = V T            Eq 1
480 km =  (V-8) (T+3)  = VT -8T +3V -24      --- eq  2
equating both equations we get
     - 8 T + 3V -24 = 0
      - 8 (480/V) + 3 V - 24 = 0        - 3840 + 3 V^2 - 24 V  = 0
           V^2 - 8 V - 1280 = 0        V = (8 +- √ 64 + 4* 1280  ) / 2  = (8 +- 72 )/2
  V = 40 KMPH neglecting -ve vakue

Answer 2

Answer:

Step-by-step explanation:

let the speed of the train = V km/h

let it travel for t hrs

A.T.Q

480 km = V*T

480 km = (v-8)(T+3)

             =VT - 8T + 3V - 24

On comparing

VT = VT - 8T + 3V -24

-8T + 3V -24 = 0

-8(480/V) + 3V - 24 = 0

-3840/V + 3V - 24 = 0

multiply V both sides

V(-3840/V +3V - 24) = V(0)

-3840 +3V^2 -24V = 0

divide both side by 3

V^2 -8V - 1280 = 0

here v is the speed of the train