lesson

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If you have 3 whole pizzas and cut each pizza in half, how many slices do you get?
You get 6 slices! Even though you divided the pizzas into pieces, the number of pieces grew because each slice is smaller than a whole.
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Dividing by 21β gave the exact same result as multiplying by 2. But why does flipping a fraction and multiplying always work?
The Two Steps Inside Every Fraction
A fraction like 32β tells you two things: cut each whole into 3 equal pieces, then gather them in groups of 2. A reciprocal is simply a fraction flipped upside down, where the numerator and denominator swap spots, like 32β becoming 23β.
Around 850 CE, Indian mathematician Mahavira was among the first to write down that dividing by a fraction is the same as multiplying by its reversed form.
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What happens when the starting amount is also a fraction instead of a whole number?
Fraction Divided by Fraction
Imagine you have 43β of a granola bar, and a single serving is 81β of a bar. We want to find 43βΓ·81β.
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Since each whole has 8 eighths, 43β of a whole has 43βΓ8=6 eighths.