We all need to check a bill from time to time.The problem is, how do you do it when you're in a rush, when
you're under pressure, and when you don't have a calculator
handy?Actually, it's not at all difficult if you know what to look
for. Here's how to do it...Example 1
---------Suppose you are ordering some building supplies and you want
to check that the price is about right before you open your
check book.You order 213 posts at $5.85 per post.These numbers can be approximated to 200 posts at .