arithmetic exercises in a sentence

1. Sixty 2nd-grade students were the participants of their study, who were asked to fill out arithmetic exercises.
2. Monker is a patient but firm drill sergeant ( disguised as a blue frog ) who leads children through some modest arithmetic exercises in the math factory.
3. If they were reliable and from an agreed common source it might make much more sense to use the potential energy figures in the main text, but they are neither so the  installed capacity figures tend to get used-although this results in regular mental arithmetic exercises if you are attempting to compare the technologies.
4. It's difficult to find arithmetic exercises in a sentence.