Question

Working together, Jacob and Kristin can

wax a floor in 6 minutes. Had she done it
alone it would have taken Kristin 10
minutes. How long would it take Jacob to
do it alone?

Answer 1

15 minutes

Explanation:

Their rate together is 1/6 floor per minute.

Her rate alone is 1/10 floor per minute.

His rate is the difference of these:

1/6 - 1/10 = 5/30 -3/30 = 2/30 = 1/15 . . . . floor per minute

It would take Jacob 15 minutes to do it alone.