It took Brian 11 hours to drive to a job interview. On the way home, he was able to increase his average speed by 12mph and make the return drive in only 9 hours. Find his average speed on the return drive.
original drive Rate, time, distance
return drive rate, time, distance
Answers
Given :- It took Brian 11 hours to drive to a job interview. On the way home, he was able to increase his average speed by 12mph and make the return drive in only 9 hours. Find his average speed on the return drive. ?
Solution :-
Let us assume that, Original speed of Brain while going for Job interview was x km/h .
so,
→ speed * Time = Distance
→ x * 11 = 11x km .
now,
→ New speed = (x + 12) km/h .
→ Time = 9 hours.
then,
→ Distance = 9(x + 12) km.
since, both distance is same ,
→ 9(x + 12) = 11x
→ 9x + 108 = 11x
→ 11x - 9x = 108
→ 2x = 108
→ x = 54 km/h .
therefore,
→ Speed while return drive = 54 + 12 = 66 km/h . (Ans.)
Hence, Brian average speed on the return drive is 66km/h .
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