Checker

Cross Multiplication Checker

Check your cross multiplication work and solve missing values in proportions.

a:b = c:d → a×d = b×c

If both products equal, the ratios form a proportion

How to use this checker

Enter a proportion as a:b = c:d. The checker verifies whether a×d = b×c and shows the work.

What this means in math class

Cross multiplication is the standard verification method. Teachers expect to see a×d = b×c written out.

Worked examples

Example 1: Valid proportion

2:3 = 4:6

Step 1:Cross multiply: 2 × 6 = 12
Step 2:Cross multiply: 3 × 4 = 12
Step 3:12 = 12, so these are proportional

Answer: ✅ 2:3 = 4:6 is a valid proportion

Example 2: Invalid proportion

2:3 = 5:7

Step 1:Cross multiply: 2 × 7 = 14
Step 2:Cross multiply: 3 × 5 = 15
Step 3:14 ≠ 15, so these are NOT proportional

Answer: ❌ 2:3 ≠ 5:7

Frequently asked questions

How do I check cross multiplication?

Multiply the outer terms and inner terms. If they're equal, it's a proportion.

Does order matter?

Yes. a:b = c:d means the first ratio compares to the second.

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