When two fractions are equal, cross-multiplying turns them into a single equation.
Walk through
Step 1 of 4
The equation
Solve x/4 = 6/8 by cross-multiplying.
When (and how) to cross-multiply
- Use it only when you have one fraction equal to one fraction.
- a/b = c/d ⇒ ad = bc (multiply each numerator by the other denominator).
- It's really just multiplying both sides by both denominators in one move.
Your turn
Solve 5/x = 2/6.
Watch out
Cross-multiplying does not work on x/4 + 1 = 6/8 — there are two terms on the left. Combine into a single fraction first, or just multiply through by the common denominator.
Rule
Try it
x/4 = 6/8
8x = 24, so x = 3.