Question

An express train takes 30 minutes less for a journey of 440 km, if its usual speed is increased by 8 km/hr. Find its usual speed

Answer 1

expressing time in hours,
difference in time= 0.5 hour
let usual speed be x
time= distance/speed
so (440/x)-(440/(x+8))= 0.5
440{(x+8)-x}=0.5x(x+8)
440*8=0.5(x^2)+4x
0.5(x^2)+4x-3520=0
(x^2)+8x-7040=0
(x^2)+88x-80x-7040=0
(x+88)(x-80)=0
x=80

so the usual speed is 80 kmph

Answer 2

Answer:

The usual speed is 80 kmph.

Step-by-step explanation:

Given : An express train takes 30 minutes less for a journey of 440 km, if its usual speed is increased by 8 km/hr.

To find : Its usual speed?

Solution :

Expressing time in hours,

Difference in time= 0.5 hour

Let usual speed be x

$T=\frac{D}{S}$

According to question,

$\frac{440}{x}-\frac{440}{x+8}=0.5$

$440{(x+8)-x}=0.5x(x+8)$

$440\times 8=0.5(x^2)+4x$

$0.5(x^2)+4x-3520=0$

$(x^2)+8x-7040=0$

$(x^2)+88x-80x-7040=0$

$(x+88)(x-80)=0$

$x=80$

Therefore, The usual speed is 80 kmph.