Question

a train travelling at uniform speed for 480km would take 48 minutes more to travel that distance if speed is reduced by 20km/h find original speed of train​

Answer 1

Let the speed be x
So
480/x - 480/x-20 = 48
( time = distance/ speed )
So we get an quadratic equation..
By using quadratic formula u can find answer..

Answer 2

Given:

A train travelling at uniform speed for 480km would take 48 minutes more to travel that distance if speed is reduced by 20km/h ,

To Find:

Find original speed of train​

Solution:

Let the speed of train be x

Distance = 480 km

Formula:

$Time = \frac{Distance}{Speed}$

So, $Time = \frac{480}{x}$

Now speed is reduced by 20 km/hr

So, $Time = \frac{480}{x-20}$

Since we are given that A train travelling at uniform speed for 480km would take 48 minutes more to travel that distance if speed is reduced by 20km/h ,

So,$\frac{480}{x-20}-\frac{480}{x}=\frac{48}{60}\\\frac{480x-480x+9600}{(x-20)x}=\frac{480}{60}\\\frac{9600}{(x-20)x}=\frac{480}{60}\\x=-100,120$

Since the speed cannot be negative

So, Speed of train = 120 km/hr

Hence The original speed of train is 120 km/hr