If a car reduces its speed by 10 km/h, it takes 1 hour more for a journey of 300 km. Find original speed.
Show answer & explanation
Correct answer: B
Explanation
Given:
Distance = 300 km
Reducing speed by 10 km/h results in 1 hour more time
Formula:
Time = Distance / Speed
Let initial speed = x km/h
Initial time = 300 / x
New speed = x − 10
New time = 300 / (x − 10)
Conditionally:
300/(x − 10) − 300/x = 1
LCM = x(x − 10)
300x − 300(x − 10) = x(x − 10)
300x − 300x + 3000 = x² − 10x
x² − 10x − 3000 = 0
x² − 60x + 50x − 3000 = 0
x(x − 60) + 50(x − 60) = 0
(x − 60)(x + 50) = 0
x = 60 km/h