Date: 10/19/98 at 16:54:41 From: LEE Subject: Decimals Hi, My name is Lee. For the past few days, we have been learning decimals, and I don't understand them that well. What should I do?
Date: 10/19/98 at 20:45:54 From: Doctor Sam Subject: Re: Decimals Hi Lee! Have you asked your teacher for extra help? I think finding another person to talk to is best. But in the meantime, maybe this will help a little. When I think of decimals I sometimes think about money. Not all kinds of money, just certain kinds. For bills: $100 bills, $10 bills and $1 bills. For coins: pennies and dimes. A decimal is a number that looks like this: 24.31 or 154.7 The "." is called the decimal point and it separates the decimal into two parts. The part on the left is an ordinary whole number, like 24 or 154. The part on the right is really a fraction, but never in quarters or thirds, always tenths or hundredths. Here is why I think about money. I can think about 154 this way: 1 hundred dollar bill + 5 ten dollar bills + 4 one dollar bills You can always break up any whole number this way. (Of course, bigger whole numbers have thousands and millions and there aren't bills that big, so money will only work with smaller numbers.) I can think about the digits to the right of the decimal point this way: .56 means 5 dimes and 6 pennies That's because a dime is one-tenth of a dollar and a penny is one-hundredth of a dollar. So 176.28 means 1 (100) + 7 (10) = 6(1) + 2(tenths) + 8 (hundredths). Now decimal numbers can have lots more digits to the right (like 4.51728) but we only have dimes and pennies, so you can't think about money to help you with those numbers. But all decimal numbers are made up of whole number parts to the left of the decimal and fractional parts to the right. The whole numbers are always ten times bigger as you move to the left: --------------- ----------- ----------- --------------- . thousands hundreds tens ones place place place place 1000 = 10 x 100 100 = 10x10 10 = 10 x 1 1 = 10 x (1/10) and the fractions to the right of the decimal are all ten times smaller as you go to the right: . ------------ ------------ ------------- tenths hundredths thousandths place place place 1/10 = 1/100 = 1/1000 = 1 divided by 10 1/10 divided by 10 1/100 divided by 10 I hope that helps! - Doctor Sam, The Math Forum http://mathforum.org/dr.math/
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