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May 2012

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Dividing Fractions 2a: How Many Times Does It Fit?

The video below shows two kinds of examples of fraction division where we do not have to use the "rule", but instead can use "mental math". The first type is dividing fractions by whole numbers. The second is divisions where the answer is a whole number, and we can think "How many times does it (the divisor) fit into the dividend?"

How many times does one thing fit into another? From this situation, you can always write a division, and think: "How many times does the divisor go into the dividend?"
How many times does  1 4  go into  2? How many times does   go into  ? 8 times. We write a division:  2 ÷ 1 4  = 8	How many times does  1 2  go into  3? How many times does   go into  ? 6 times. We write a division:  3 ÷ 1 2  = 6

1. Solve. Write a division.

a. How many times does  1 3  go into  2?     How many times does   go into  ? 2 ÷ 1 3  =
	f. [available in the book]
g. [available in the book]	h. [available in the book]

2. Divide. Think “How many times does (the divisor) go into (the dividend)?” Use pictures to help.

a.   3 ÷ 1 6 = b.   3 ÷ 2 6 =	[available in the book]
g.   3 ÷ 1 2 =		[available in the book]

4. Solve. Use the shortcut.

The ideas in this fraction lesson are taken from the Math Mammoth Fractions 2 book. Only a few examples of each problem type are shown; you should make more problems of each kind for the student.

Math Mammoth Fractions 2 A self-teaching worktext that teaches fractions using visual models, a sequel to Math Mammoth Fractions 1. The book covers simplifying fractions, multiplication and division of fractions and mixed numbers, converting fractions to decimals, and ratios. Available as an affordable download ($5.00), and also as a printed copy. => Learn more and see the free samples! See more topical Math Mammoth books

Next lesson: Reciprocal Numbers