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Solve proportions using cross multiplication
Solve proportions of the form a:b = c:d. Leave one value empty to find the unknown using cross multiplication.
Leave one field empty to solve for that value
Enter 3 values to solve for the 4th
A proportion states that two ratios are equal. The proportion a:b = c:d can also be written as a/b = c/d. Cross multiplication (ad = bc) is used to solve for an unknown value.
If a:b = c:d, then a × d = b × c
Multiply the outer terms and inner terms to get equal products.
3:4 = 6:8
3 × 8 = 24 and 4 × 6 = 24 ✓
A proportion is an equation stating that two ratios are equal. For example, 2:3 = 4:6 is a proportion. It can also be written as fractions: 2/3 = 4/6.
Cross multiplication uses the property that if a/b = c/d, then a×d = b×c. You multiply diagonally across the equal sign. This is the fastest way to solve proportions.
Proportions are used in cooking (scaling recipes), maps (scale ratios), unit conversion, mixing solutions, comparing prices, calculating percentages, and many other everyday situations.
Yes, proportions can involve negative numbers. The cross multiplication method works the same way regardless of whether the numbers are positive or negative.
A ratio compares two quantities (like 2:3), while a proportion states that two ratios are equal (like 2:3 = 4:6). A proportion is an equation involving two ratios.
Use cross multiplication. If a:b = c:d is correct, then a×d should equal b×c. For example, in 3:5 = 6:10, check: 3×10 = 30 and 5×6 = 30, so it's correct.
Yes! If you know three values in a proportion, you can always solve for the fourth using cross multiplication, whether it's represented by x, y, or any other variable.
The same cross multiplication method works. Just multiply carefully. For example, if 1/2:3/4 = x:6, then (1/2)×6 = (3/4)×x, which gives 3 = (3/4)x, so x = 4.