Ratio Calculator
Solve a : b = c : x for x.
How it works
x = b × c ÷ a
Proportions are solved by cross-multiplication: a·x = b·c, so x = b·c ÷ a.
Worked example
Given 3 : 4 = 15 : x, x = 4 × 15 ÷ 3 = 20.
Split 60 in the ratio 2:3: five parts, 12 each, giving 24 and 36.
Notes and limitations
The key property: multiplying or dividing both sides keeps the ratio. For sharing problems, find the total number of parts first. Remember a:b corresponds to a/(a+b) as a fraction.