Pre-Algebra · Ratios, rates and proportions

How to Simplify a Ratio

Problem

18:2418 : 24

Answer

3:43 : 4

A ratio compares two quantities. Simplifying a ratio is like simplifying a fraction: divide both parts by the greatest common factor.

Step-by-step solution

  1. Find the greatest common factor of 18 and 24.

    gcd⁡(18,24)=6\gcd(18, 24) = 6

    Why: Dividing by the largest shared factor simplifies the ratio in one step.

  2. Divide both parts by 6.

    18÷6=3,24÷6=418 \div 6 = 3,\quad 24 \div 6 = 4

    Why: Both parts must change together so the ratio keeps its value.

  3. Write the simplified ratio.

    3:43 : 4

    Why: 3 and 4 share no factor larger than 1, so the ratio is in lowest terms.

Common mistakes

  • Subtracting 18 from 24 instead of dividing. A ratio simplifies by division.
  • Dividing only one side. Both parts need the same divisor.
  • Flipping the order. The first quantity stays first.

Practice problems

Use the same method. Work each problem on paper, then open the answer to check.

  1. 15:2515 : 25

    Show answer

    3:53 : 5

  2. 16:2416 : 24

    Show answer

    2:32 : 3

  3. 27:3627 : 36

    Show answer

    3:43 : 4

  4. 35:4235 : 42

    Show answer

    5:65 : 6

  5. 44:6644 : 66

    Show answer

    2:32 : 3