the distance of the college and home of rajeev is 80km one day he was | Examsbook

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Q: 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?

1
28 km/h
2
30 km/h
3
40 km/h
4
20 km/h

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Answer : 4. "20 km/h"
Explanation :
Answer: D) 20 km/h Explanation: Let the normal speed be x km/h, then 80x-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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