===========================================================A Rough Guide to Everyday Mental Calculation!
(c) Copyright 2004 by Murdo Macleod
===========================================================
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
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 $6 per post.
Multiplying 200 and 6 is easy: expected bill should be about $1200.
Basically you just look at figures and round them to nearest convenient unit. (That's why we approximated $5.85 to $6).
Example 2 ---------
Similarly for 330 pieces of turf @ 65 cents each, just find 300 × 70 = 21000 cents = $210.
