Copy of Estimating Sums

Estimation problem like what might be seen on mathleague.org Number Sense Exam (among their Elementary Contest tests). Need to get the answer to within 5% of the exact answer. The goal is to quickly come to an estimate within 5%, not to spend the extra time to get the exact answer.
Estimation problem like what might be seen on mathleague.org Number Sense Exam (among their Elementary Contest tests). Need to get the answer to within 5% of the exact answer. The goal is to quickly come to an estimate within 5%, not to spend the extra time to get the exact answer.