Question

Maxine spent 15 hours doing her homework last week. This week she spent 18 hours doing homework. She says that she spent 120% more time doing homework this week. Is she correct? Show your work to justify your decision

Answer 1

Maxine is incorrect.

Explanation:

18 - 15 = 3 3/15 = 0.2 0.2(100) = 20.

20% is the percent of increase. 120% would be the total of both combined. Since we are only looking for how much more, it would be 20%.

Answer 2

The best way to solve this problem is to use the 'rule of three":

If 15% correspond to 100%

then 18% correspond to X%

We notice that both lines are in the following proportion:

(15) / (100%) = (18) / (X%)======> X%= (18 x 100%) / 15= 6/5 = 1.2 =120%