Q&A #854

Adding fractions

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From: Marielouise (for Teacher2Teacher Service)
Date: Nov 29, 1998 at 21:39:41
Subject: Re: Adding fractions

Consider the following problem. It should illustrate for you why you have to use a common denominator. I suggest that you do this with a classroom of kids. Cut out large circles to represent the pizza. Cut the circles into the number of pieces mentioned. Gather up the remainders and ask the students to determine how much of the original 7 pizzas remain. The Problem: Suppose your classroom had a pizza party. You ordered 7 large pizzas. Originally the pizzas were not cut into the same size pieces. Three of the pizzas were cut into four equal-sized pieces each, another two into six pieces each, another one in eight pieces each and another into twenty-four pieces, because everyone wanted to try an anchovy pizza! When the room was being cleaned up some of every type of pizza was left over. There were five pieces left from every type of pizza. However, among the 20 pieces it is obvious that they were not all the same size. The question is: How much total pizza was left? Hopefully, they will be able to understand that the five pieces left from the anchovy pizza is less than one of the pieces from the pizza cut into four and more than one piece from the pizza cut into eight. Enjoy this problem. It should keep a class occupied for some time. - Marielouise, for the Teacher2Teacher service

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