Question

Shantanu drives a motorcycle and covers a distance of 715 km at a constant speed. If the speed of the `motorcycle had been 10 km/h more, he would have taken 2 h less to cover the same distance. What is the original speed of the motorcycle ?

Answer 1

Explanation:

Given Shantanu drives a motorcycle and covers a distance of 715 km at a constant speed. If the speed of the `motorcycle had been 10 km/h more, he would have taken 2 h less to cover the same distance. What is the original speed of the motorcycle ?

• Let the constant speed be x
• According to question, 715 / x – 715 / x + 10 = 2
• So 1/x – 1/x + 10 = 2/ 715
• So x + 10 – x / x (x + 10) = 2/715
• So x^2 + 10 x = 715 x 5
• So x^2 + 10 x – 3575 = 0
• So x^2 + 65 x – 55 x – 3575 = 0
• So x (x + 65) – 55(x + 65) = 0
• So (x – 55) (x + 65) = 0
• So x = - 65 , 55

Therefore original speed of the motorcycle is 55 km /hr