# Divide by Fractions

Divide by Fractions
We will divide whole numbers by fractions.
Examples:
1).

Step 1: When dividing a whole number by a fraction change the whole number to a fraction by placing it over 1.

Step 2: Use KCF (Keep, Change, and Flip) when dividing fractions. Keep 6/1, change division to multiplication, and Flip 1/3 to 3/1.

Step 4: Multiply numerators, 6 x 3= 18 and multiply denominators, 1 x 1= 1 and simplify if needed.

We will divide fractions.

2).

Step 1: Use KCF (Keep, Change, and Flip)

when dividing fractions. Keep 1/4, change division to multiplication, and flip 3/8 to 8/3.

Step 2: Multiply numerators, 1 x 8=8 and multiply denominators, 4 x 3=12.

Step 3:Simplify using GCF

Find GCF:

Factors of 8 :1,2,4, and 8

Factors of 12:1,2,3,4,,6, and 12

Common factors of 8 and 12: 1,2, and 4. Although all bold numbers are common factors of 8 and 12, 4 is the greatest common factor. We divide the numerator and denominator by 4.

We will divide mixed numbers

3).

Step 1: First, we need to change both mixed numbers to improper fractions.

Step 2:Use KCF (Keep, Change, and Flip) when dividing fractions. Keep 21/5, change division to multiplication, and flip 7/3 to 3/7.

Step 3: Multiply numerators, 21 x 3= 63 and multiply denominators, 5 x 7=35.

Step 4: Simplify using GCF

Find GCF.

Factors of 63: 1, 3, 7, 9, 21, and 63

Factors of 35: 1, 5, 7, and 35. Although all bold numbers are common factors of 63 and 35. 7 is the greatest common factor. We divide the numerator and denominator by 7.

Step 3: We have to change the improper fraction 9/5 to a mixed number. 5 can go evenly into 9 only once with a remainder of 4. The denominator does not change. 1 is the whole number and the remainder 4 is the numerator.

Videos:

Found on the Web:

PowerPoint:

Dividing Fractions

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### Figure This Challenge #56

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Created by Wanda Collins May 10, 2015 at 1:56pm. Last updated by Wanda Collins May 10, 2015.

# Math Limerick

Question: Why is this a mathematical limerick?

( (12 + 144 + 20 + 3 Sqrt[4]) / 7 ) + 5*11 = 92 + 0 .

A dozen, a gross, and a score,
plus three times the square root of four, divided by seven, plus five times eleven, is nine squared and not a bit more.

---Jon Saxton (math textbook author)

Presentation Suggestions:
Challenge students to invent their own math limerick!

The Math Behind the Fact:
It is fun to mix mathematics with poetry.

Resources:

Su, Francis E., et al. "Math Limerick." Math Fun Facts.

funfacts

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