Multiplying Decimals by NegativesDate: 03/18/2002 at 21:25:47 From: Miki Subject: How to multiply decimals by negatives How do you multiply negatives by decimals? I can't find decimals on my calculator. My exact problem is .56 times -50. Is there even an answer? Date: 03/19/2002 at 09:43:17 From: Doctor Rick Subject: Re: How to multiply decimals by negatives Hi, Miki. Do you know how to multiply 56 by -50? You multiply 56 by 50, then give the answer a negative sign because the signs of the two factors are different. If the signs were the same (either both positive or both negative), the product would be positive. 56 * 50 = 2800 56 * -50 = -2800 Do you know how to multiply 0.56 by 50? First multiply 56 by 50, then move the decimal point two places to the left, because that's what you do to change 56 to 0.56. If both factors had digits to the right of the decimal point, you'd move the decimal point of the product to the left as many places as there were digits to the right of the decimal points in the two factors combined. 56 * 50 = 2800 0.56 * 50 = 28.00 We can do both at once. To multiply 0.56 by -50, you first multiply 56 by 50. Then you put a negative sign on the product, AND you move the decimal point two places to the left. 56 * 50 = 2800 0.56 * -50 = -28.00 Now, about the calculator. I have never seen a calculator (unless it was one we made in a programming class) that did not have a decimal point. Just enter . 5 6 The negative number may be tricky. Many computers don't let you enter - 5 0 in that order to enter a negative number. Instead you have to enter 5 0 +/- That +/- is a single key that changes the sign of the number in the display. After you press it, the display will read -50. Thus the complete calculation is entered as . 5 6 * 5 0 +/- = on most calculators I have seen. (* is the multiplication sign.) - Doctor Rick, The Math Forum http://mathforum.org/dr.math/ |
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