2012-03-28 09:00:35

During his second week of mowing lawns, William earned $200. This represented a 300% increase over the amount he earned in his first week of work. If on the third week of work, he increased his earnings by 50% of his week two earnings, how much more money did he make in week three of mowing lawns than he did in week one?

(A) $150.67
(B) $233.34
(C) $250
(D) $300
(E) $350

The correct answer is C

Explanation: Start by finding out how much money William earned in his first week of mowing lawns. If $200 is a 300% increase from his first week’s earnings, then $200 is 400% of what he earned in the first week (since percent increase is calculated as the difference between the original amount and the final amount, and 400 - 300 = 100%). Let x = the amount he earned in that first week, then. If $200 is 400% of that amount, then 400%x = 200, meaning 4x = 200, meaning x = $50 (since 200/4 = 50).

Now, calculate how much William earned in his third week of mowing lawns by finding how much money a 50% increase of $200 is. A 50% increase of a number means the new number is 150% of the original number, meaning 1.5(200) will provide William’s third week earnings. 1.5(200) = $300.

Finally, calculate the difference between WIlliam’s third and first week earnings by subtracting 50 from 300 to get $300 - $50 = $250, making choice C correct.