#412. Fractions unit introduction

Mathematics, level: Elementary
Posted Sat Apr 25 19:44:41 PDT 1998 by Mr. Blaine Scott (bmscott@csolve.net).
Sacred Heart School, Midland ON Canada
Materials Required: modelling clay, plastic knife, roller
Activity Time: 40-60 minutes
Concepts Taught: Fractions

Grades 2-4
Math Fractions unit introduction:

Materials needed. Cookie cutter shape for each student (use yogurt cups, something small and round) a ball of plasticene (modelling clay), and a plastic disposable knife, a 6 cm piece of 2cm diameter wood doweling or a small rolling pin for each student.

Aim: to understand the concepts behind fractions:
a) when comparing whole amounts, each whole has to be of equal value
b) the denominators of fractions remain the same when adding or subtracting fractions
c) equivalent fractions
d) multiplying fractions the answers get smaller, dividing by fractions the quotient gets bigger.

Strategy: pass out the plasticene and tell the students to flatten it out into a pancake 1/2 a cm thick and big enough to cut 2-3 shapes using the cookie cutter they have.

Tell them to cut at least two whole shapes out of the plasticene and ask them to cut one of them in half and one of them in quarters. Question them about the importance of equal parts within the whole: If the parts are not equal is the whole divided up into proper fractions, why or why not. Compare the half to the quarters. Write 1/2 on the board. Ask how many quarters = it. Discuss equivalent fractions
Write 1/2 + 1/2 = (1) 2/2 Ask students to make up equivalent fraction examples in plasticene for thirds, quarters, fifths, sixths, eighths, and tenths.
Tell them to vary the shape of the whole: rectangles, squares, circles.
Invent your own set of instructions so as to demonstrate the aims above.

Tasks: Have the students demonstrate fraction sentences by writing the sentence on a piece of paper and have the plasticene shapes that demonstrate each fraction below on the paper.
Create 3D effects by forming the clay into rope and cutting it up. The pieces become more manipulative.

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