Question

A freight train completes its journey of 150 miles 1 hour earlier if its original speed is increased by 5 miles/hour. what is the train's original speed? 20 miles/hour 25 miles/hour 30 miles/hour 35 miles/hour

Answer 1

let  x = original speed
x + 5 = increased speed
travel time=distance/speed

150  / x     - 150  /  x+ 5 = 1

common denominator :x(x+5)
150(x+5)-150x=x(x+5)
150x+750-150x=x^2+5x
x^2+5x-750=0
(x-25)(x+30)=0
x=25