Multiplying and Dividing DecimalsDate: 6/27/96 at 15:0:51 From: Sue Paul Subject: Decimal Division, Multiplication Dear Dr. Math, I am going into Grade 6 next September. On my report card my teacher commented that I have difficulty with multiplication and division of decimals. Would you please explain these concepts? Thank you, Chris Paul Date: 7/28/96 at 13:25:1 From: Doctor Robert Subject: Re: Decimal Division, Multiplication Hi Chris, When multiplying decimals you follow this simple rule. Multiply the numbers totally disregarding the decimal points - that is, treat the numbers as if they were whole numbers. Then, after you have done the multiplication, count the number of digits to the right of the decimal in each of the numbers. ADD these numbers together and then count off (from the right) this number of places in the answers and put the decimal point there. An example will help: 27.8 x 2.345 First multiply 278 x 2345 which is 651910. Now, in the first number there is ONE place to the right of the decimal and in the second number there are THREE digits to the right of the decimal. ONE plus THREE = 4. Therefore, count four places in from the right of the answer. The answer should be 65.191. To divide, you do the following. Move the decimal point in the DIVISOR to the right until the number becomes a whole number. Move the decimal point the SAME NUMBER of places in the dividend. Then proceed to divide the way you would with whole numbers. The decimal point in the answer lies directly above the decimal point in the dividend. An example: 27.84 divided into 434.6. Move the decimal TWO places in both numbers. The problem then becomes: 2784 divided into 43460. The answer is 15.6106... I hope that this helps. -Doctor Robert, The Math Forum Check out our web site! http://mathforum.org/dr.math/ |
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