Multiplying Whole Numbers by Fractions
Date: 05/31/99 at 17:22:28 From: Lemarcus McCakk Subject: Fractions How do you multiply whole numbers by fractions?
Date: 06/01/99 at 12:57:53 From: Doctor Rick Subject: Re: Fractions Hi, Lemarcus. I have 3 of those new quarters with Caesar Rodney on the back. If you have 5 times as many of them as I have, how many do you have? 3 quarters x 5 = 15 quarters. Let's write that in dollars: 1 quarter is 1/4 dollar, so 3 quarters = 3/4 dollar. 3/4 x 5 = 15/4 Do you see what I did? I just multiplied the numerator of the fraction (3) by the whole number (5) to get the new numerator. Then you can rewrite the improper fraction as a mixed fraction: 15/4 = 3 3/4 Here is another way to think about it, if you're familiar with multiplying fractions. When you multiply two fractions together, you multiply the numerators to get the new numerator, and you multiply the denominators to get the new denominator. If you have a whole number instead of a fraction, you can rewrite it as "oneths" with a denominator of 1. Then you can multiply using the rule for multiplying fractions. For instance, 5 = 5/1 3 3 5 3 x 5 15 --- x 5 = --- x --- = ----- = -- 4 4 1 4 x 1 4 - Doctor Rick, The Math Forum http://mathforum.org/dr.math/
Search the Dr. Math Library:
Ask Dr. MathTM
© 1994- The Math Forum at NCTM. All rights reserved.