Jan is cutting a rectangular pan of brownies. she cut them in half and then cut each of those halves in half again. she did the same thing going the other direction. how many brownies does she have?

I drew a picture!!
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Maybe you didn't.
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I like to picture things though.
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Ok, a rectangle cut in half. 
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Ok, by definition of "half," just multiply the number of rectangles by 2.
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1 x 2 = 2 after cutting the brownies in half.
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2 x 2 = 4 after cutting it in half again.
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4 rectangles now!!
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Doing it the other way... pretend you are starting over from scratch.
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A new batch of brownies!
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But still pay attention to what you already cut. 
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Cut down the middle the other direction.
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What's 4 x 2?
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8.
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Now, finally, we multiply the half of the half brownies.
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What's 8 x 2?
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16.
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16 slices.