Question

A train travels at a certain average speed for a distance of 63 km and then travels a distance of 72 km at an average speed of 6 km/h more than its original speed. If it takes 3 hours to complete the total journey, what is its original average speed?

Answer 1

LET the original speed of train=xkm/hr.

then time taken to travel 63km=63x/hr.

new speed=(x+6)km/hr.

time taken to travel 72 km=72/(x+6)hr.

A/Q

$\frac{63}{x} + \frac{72}{x + 6} = 3 \\ \frac{63x + 378 + 72x}{ {x }^ {2 } + 6x} = 3 \\ 135x + 378 + = {3x}^{2} + 18x \\ {3x}^{2} - 117x - 378 = 0 \\ \\ {x }^{2} - 39x - 126 = 0 \\ (x - 42)(x + 3) = 0 \\ x = - 3 \: or \: x = 42$

as the speed cannot be negative x=42

thus the average speed of train is 42km/hr.

I think it helps u..

plz.. mark it as brainlist answer

Answer 2

hey mate..

here is your answer...

refer to the aatachment