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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