SOLUTION: need to help grandson with this. find missing numbers in the proportions such as. 4/7 = /28 also 1/4 = /16 2/9 = /18

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Question 19520:
need to help grandson with this.
find missing numbers in the proportions such as.
4/7 = /28 also 1/4 = /16 2/9 = /18

Answer by MelanieBCC(40) About Me  (Show Source):
You can put this solution on YOUR website!
easiest way is to cross multiply. (I'm using x for the blanks because the math writing program won't let me have blanks in an equation)
4%2F7=x%2F28 is the same as 4%2A28=7%2Ax The 4 is from the top of the first fraction, 28 from the bottom of the second fraction, 7 from the bottom of the first, and x from the top of the second
so it becomes 112=7x so it's asking, "7 times what number is 112?" solved by dividing 112 by 7 which equals 16.
Here's the set-up for the others:
1*16=4*(?), 2*18=9*(?)