SOLUTION: If the average speed for a trip is reduced by 20%, by what percent does the time change?

Algebra ->  Average -> SOLUTION: If the average speed for a trip is reduced by 20%, by what percent does the time change?      Log On


   

Question 1118007: If the average speed for a trip is reduced by 20%, by what percent does the time change?
Found 2 solutions by Alan3354, greenestamps:
Answer by Alan3354(69443) About Me  (Show Source):
Answer by greenestamps(13200) About Me  (Show Source):
You can put this solution on YOUR website!


Use fractions instead of percentages when working problems like this.

distance = rate times time

If the distance is the same, then the rate (speed) and time are inversely proportional. If the speed is lower, the time is longer by the same factor, and vice versa.

Reducing the speed by 20% means the new speed is 80% of what it was. 80% as a fraction is 4/5.

To cover the same distance at a rate 4/5 as fast, the time required is 5/4 as much. 5/4 as a percentage is 125%, which is 25% above 100%. So the time increases by 25%.