Question

Why do you cross-multiply when you solve proportions?

Answer 1

When students cross multiply while solving a proportion, they are really multiplying both sides of the equation by the products of the two denominators. What happens is that each denominator cancels one of the factors on each side, so that it seems as if you have just crossed multiplied

Hope this helps!

Answer 2

Explanation:

since the cross multiples are equal, you find a product and use the inverse operation as you would in an equation

Example 4 is to 36 as 3 is to X: 4/36 = 3/X --> 4*X = 3*36. Divide both sides by 4, to solve for X = 27.

is over of = percent of 100

is/of=%/100

What is 10% of 40.

is = x

x/40 = 10/100

cross mulitply 40*10= 400/100=4 x=4

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