SOLUTION: A motorist took 2 hours to travel from one town to another town and 1 hour 40 minutes to travel back. calculate the percentage change in the speed of the motorist.

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Question 1101378: A motorist took 2 hours to travel from one town to another town and 1 hour 40 minutes to travel back. calculate the percentage change in the speed of the motorist.
Found 2 solutions by josgarithmetic, greenestamps:
Answer by josgarithmetic(39621) About Me  (Show Source):
You can put this solution on YOUR website!
d, distance either way

d%2F2 and d%2F%281%262%2F3%29

Speed increased for going back.

%281%2F%281%262%2F3%29%29%2F%281%2F2%29

%281%2F%285%2F3%29%29%2F%281%2F2%29

%283%2F5%29%2A2

6%2F5

1%261%2F5, meaning trip going back was 20% higher speed.

Answer by greenestamps(13203) About Me  (Show Source):
You can put this solution on YOUR website!


The distance there is the same as the distance back.
That means the ratio of the speeds is the reciprocal of the ratio of the times.
The ratio of the times there and back is 6:5, so the ratio of the speeds there and back is 5:6.

The problem asks for the percent increase in speed on the way back:
6/5 = 1.2 = 120%
The return speed is 120% of the speed going; it is 20% faster than the speed going.