SOLUTION: Solve for x in the following proportion: 3/5 = 18/x

Question 465926: Solve for x in the following proportion: 3/5 = 18/x

Answer by bucky(2189) (Show Source): You can put this solution on YOUR website!
The way that I use to solve these problems is to form two products and set them equal. The products are these:
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First product -- multiply the numerator (top) on the left side by the denominator (bottom) on the right side.
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Second product -- multiply the numerator (top) on the right side by the denominator (bottom) on the left side.
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This is commonly called cross multiplication because if you draw both lines from the top of one side to the bottom of the opposite side the two lines cross like the letter x. The multiplication takes place along those two lines.
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Set these two products equal and solve. This method will work no matter in which of the four possible positions (two numerators and two denominators) the letter variable (in this case X) appears.
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For this problem:
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Cross multiply. First the 3 times the X to get 3X. Then the 18 times the 5 to get 90. Set these products equal and you have:
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Solve for X by dividing both sides of this equation by 3 and you get:
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That's the answer. Hope this method helps you to remember a consistent way that you can solve proportion problems such as these. Good Luck!!!

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