To divide a fraction by a whole number, multiply the denominator (the bottom number) by that whole number and keep the numerator the same. This works because dividing means splitting each piece you already have into smaller, equal parts.
\[\frac{a}{b} \div n = \frac{a}{b \times n}\]
Example 1 — \(\frac{3}{4} \div 2\)
Step 1
Multiply the denominator by 2: \(\frac{3}{4 \times 2} = \frac{3}{8}\)
3 cancels: \(\frac{1}{8} \times \frac{4}{1}\). Then 4 and 8 cancel: \(\frac{1}{2} \times \frac{1}{1}\)
Answer
\(\mathbf{\frac{1}{2}}\)
⚠ Common mistake: Students sometimes flip the first fraction instead of the second. Always flip the divisor (the number you are dividing by — the one after ÷).
✓ Quick Check 2 — The KCF Rule
Question 1 of 10
Mixed Numbers and Multi-Step Real-Life Problems
For mixed numbers: convert to improper fractions first, then apply KCF. Real-life problems often need an extra step — set up the division carefully before calculating.
Use KCF to work out each division. Simplify your answer. Click Check All when done.
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Question
Answer
Result
1
½ ÷ ¼
2
2/3 ÷ 4/9
3
2½ ÷ 1¼
4
¾ ÷ ⅜
5
1/3 ÷ 2/9
6
3 ÷ ¼
7
4/5 ÷ 2/5
8
1½ ÷ ¾
9
5/6 ÷ 5/12
10
2¼ ÷ ¾
⚠ Things to Watch Out For
Not flipping the right fraction: Keep-Change-Flip (KCF): keep the first fraction, change ÷ to ×, flip ONLY the second fraction. 2/3 ÷ 4/5 = 2/3 × 5/4. Do not flip the first fraction.
Flipping then forgetting to multiply: After applying KCF, you still need to multiply. The flip converts division into multiplication — then complete the multiplication step.
Dividing by a whole number: 3/4 ÷ 2 = 3/4 ÷ 2/1 = 3/4 × ½ = 3/8. Write whole numbers as fractions over 1 before applying KCF.
Not simplifying the final answer: After dividing, always check if the result simplifies. 10/12 = 5/6.
Mixed numbers: Convert to improper fractions BEFORE dividing. Never apply KCF to mixed numbers directly.