Dividing Fractions
Dividing fractions involves finding how many times one fraction fits into another fraction. The standard method requires converting division into multiplication by using the reciprocal of the divisor. This operation appears in Year 6 of the UK National Curriculum and forms a foundation for algebraic manipulation in later mathematics.
Why it matters
Dividing fractions appears frequently in real-world calculations involving rates, recipes, and measurements. A baker dividing 34 kg of flour into portions of 18 kg each needs to calculate 34 ÷ 18 = 6 portions. Construction workers dividing a 23 metre plank into 16 metre sections use the same principle. In GCSE mathematics, fraction division connects to solving equations with fractional coefficients and working with rational expressions. Engineering applications include calculating gear ratios, where 58 ÷ 14 = 2.5 represents the relationship between rotating components. Medical dosage calculations often require dividing fractional amounts, such as determining how many 13 mg doses fit into a 23 mg tablet. The reciprocal method also provides groundwork for understanding division of algebraic fractions in A-level mathematics.
How to solve dividing fractions
Dividing Fractions
- Keep the first fraction.
- Flip the second fraction (reciprocal).
- Multiply. Simplify.
Example: 23 ÷ 45 → 23 × 54 = 1012 = 56.
Worked examples
12 / 14 = _______
Answer: 2
- Invert and multiply → 12 x 41 = 42 — Flip the second fraction, then multiply across.
- Simplify → 2 — Reduce to lowest terms.
- Verify → 2 ✓ — Answer.
A rope is 45 m long. You cut it into pieces 15 m each. How many pieces?
Answer: 4
- Invert and multiply → 45 x 51 = 205 — Cutting into equal pieces is division. Flip the second fraction, then multiply across.
- Simplify → 4 — Reduce to lowest terms.
- Verify → 4 ✓ — Answer.
23 / 15 = _______
Answer: 3 13
- Invert and multiply → 23 x 51 = 103 — Flip the second fraction, then multiply across.
- Simplify → 3 13 — Reduce to lowest terms.
- Verify → 3 13 ✓ — Answer.
Common mistakes
- Dividing numerators and denominators separately, writing 2/3 ÷ 4/5 = (2÷4)/(3÷5) = 1/2 ÷ 3/5 instead of the correct answer 5/6
- Forgetting to flip the second fraction, calculating 1/2 ÷ 1/4 as 1/2 × 1/4 = 1/8 instead of 1/2 × 4/1 = 2
- Converting division to multiplication but flipping the wrong fraction, writing 3/4 ÷ 2/5 = 4/3 × 2/5 = 8/15 instead of 3/4 × 5/2 = 15/8