Answer:

Explanation:
GIVEN: In a
mile race, Janet covered the first
miles at a constant rate. She then speed up and rode her bike the last
miles at a rate that was
miles per minute faster. Janet's overall time would have been
minutes faster had she ridden her bike the whole race at the faster pace.
TO FIND: What was Janet's average speed (in miles per minute) for the whole race?
SOLUTION:
let the speed of Janet in first

speed of Janet's bike in last

total time taken by Janet,


Time taken if Janet rides whole race at faster pace

As, Janet's overall time would have been
faster had she ridden her bike the whole race at the faster pace.




on solving we get





Average speed

Average speed

Therefore average speed of Janet was
