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Using Multiplicative Inverse to Solve Equations, a la Shmoop.

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Whenever there's a snowstorm, hailstorm, windstorm, sandstorm, any kind of storm...

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... your parents go a little crazy stocking up on canned goods.

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Right now, the stack of cans in the basement is about eleven feet high...

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Your basement's pretty roomy. Its ceiling is twenty feet high. You could play basketball

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down there...

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If it weren't for all the hoarding.

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If the tower of cans grows three-quarters of a foot each month, how many months will

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it take for all those canned beets and carrots to reach the ceiling?

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Here are your options: First, we need to write this out in an equation.

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Let's see if we can find a piece of paper and pencil in all this junk.

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Okay, so we'll describe this as...

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Current height of the cans...

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Plus growth rate...

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Times number of months... for which we'll use M as the variable -- notice the clever

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first letter thing there -

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Equals height of the ceiling which is 20 feet. We're solving for number of months, so that

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value is M

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Here's our finished equation: First, we need to subtract eleven from each

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side.

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We know you wish you could subtract that eleven-foot-stack of canned peas from your life, but this is

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just hypothetical. Sorry.

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That leaves us with three-fourths X on the left and nine on the right.

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In order to get rid of the fraction, we need to multiply each side by the inverse of the

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fraction.

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Inverse means to flip the fraction over, kind of like multiplying by its opposite.

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Just like you want to live in a house that isn't filled with horded emergency supplies.DELETE

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In this case, the multiplicative inverse would be four over three. So multiply both sides

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by four over three. That cancels out the three-fourths on the

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left, leaving us with X.

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Multiply nine by four over three to get thirty-six over three.

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Simplify that to get twelve. The answer is B, X equals twelve. So it looks

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like you have a year before your basement is totally full.

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Look at the bright side. If a disaster does wipe out your house, you can live in a can

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fort. Food and shelter in one convenient place.

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Plus, you now have the invaluable survival skill of Using Multiplicative Inverse to Solve

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Equations.

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We'll be at your place when disaster strikes.

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