This problem is a more like of a percentage increase problem. First, subtract 11 hours by the original hours which is 10 hours. Using mental math, subtracting 11 by 10 would be 1, obviously. Take the outcome of 1 and divide it by the hours he did last week which is 10. 1 divided by 10 would be equal to .1. Convert the decimal to a percentage and then you would get 10% and add it to 100%. So, yes, he is in fact correct.
