Question

A train travels a distance of 480km at a uniform speed. If the speed had been 8km/hr less, then it would have taken 3 hours more to cover the same distance. We need to find the speed of the train.
I promise whose ans will be correct i will make him brainliest. And also thise que is from chapter quadratic eqation. Plz help me. ​

Answer 1

Answer:

$40 \: km/h$

Step-by-step explanation:

Distance travelled by the train = 480 km

Let the speed of the train be x kmph

Time taken for the journey = 480/x

Given speed is decreased by 8 kmph

Hence the new speed of train = (x – 8) kmph

Time taken for the journey = 480/(x – 8)

480/(x – 8) – 480/x = 3

480(x – x + 8)/x (x-8) = 3

480/3 * 8 = x2 -8x

1280 = x2 – 8x

x2 – 8x – 1280 = 0

On solving we get x = 40

Thus the speed of train is 40 km/h

Answer 2

Answer:

Let speed of the train =xkm/hr

distance=480km/hr

time taken by the train to cover the distance of 480 km is equal to 480/x km/hr

now ,acc to given condition

480/x-8 -480/x =3

480( 1/x-8 - 1/x)= 3

x-8 +8/x(x-8)=3/480

x^2 - 8x =1280

x^2 -8x-1280 =0

x^2 -40 x+ 32x - 1280 =0

x(x-40) +32 (x-40) =0

x-40 = 0 or x+32=0

x=40 or x =-32

but the speed of train cannot be negative.hence the speed of the train is 40km /hr