Why Multiplying by 10 Just Adds a Zero at the End
Date: 10/18/2005 at 11:08:41 From: Jill Subject: Explanation of multiplying by 10 My daughter is learning multiplication and is having a hard time figuring out why if you add a zero to a number while multiplying by 10 it works. Her teacher is unable to get through to her and I was looking for a way to explain this better. Something concerning place value but don't know how to explain to a 8 year old!
Date: 10/18/2005 at 16:58:10 From: Doctor Peterson Subject: Re: Explanation of multiplying by 10 Hi, Jill. We may have to make a few attempts before we meet her particular style of learning, but here's my first method. Look at a number like 123. This means 100 + 20 + 3 because the 1 is in the hundreds column, the 2 is in the tens, and so on. Now put a 0 at the end, to make 1230. Suddenly the 1 has moved into the thousands column, the 2 is in the hundreds column, and so on. Every digit has been shoved over, so that it is worth 10 times what it was worth before. It's as if I took your wallet and replaced every one dollar bill with a ten, every ten with a hundred, and so on. The total is worth ten times what it was. That's what's happening here. If that doesn't work, please write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994-2013 The Math Forum