The distance of the college and home of Raj is 80km One day he was late by 1 hour than the normal ti...........

Quant (SSC) Time & distance

The distance of the college and home of Raj 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 Raj?

28 km/h

30 km/h

40 km/h

20 km/h

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Explanation:

Let the normal speed be x km/h, then
(80/x)−(80/(x+4))=1
⇒x2+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

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