Question

The distance of the college and home of Rajeev is 80km. One day he was late by 1 hour than the normal time to leave for the college, so he increased his speed by 4km/h and thus he reached to college at the normal time. What is the changed (or increased) speed of Rajeev?

A) 28 km/h B) 30 km/h C) 40 km/h D) 20 km/h

Answer 1

Answer:

20 km/h

Step-by-step explanation:

Let the normal speed be x km/h, then 

80x−80(x+4)=180x-80(x+4)=1

⇒⇒x2+4x−320=0x2+4x-320=0

⇒⇒x (x + 20) - 16 (x + 20) = 0

(x + 20 ) (x - 16) =0

 

x = 16 km/h

 Therefore (x + 4) = 20 km/h

 Therefore increased speed = 20 km/h