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 sa
me thing going the other direction.How many brownies does she have?
1 answer:
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.
.
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.
.
Maybe you didn't.
.
I like to picture things though.
.
Ok, a rectangle cut in half.
.
Ok, by definition of "half," just multiply the number of rectangles by 2.
.
1 x 2 = 2 after cutting the brownies in half.
.
2 x 2 = 4 after cutting it in half again.
.
4 rectangles now!!
.
Doing it the other way... pretend you are starting over from scratch.
.
A new batch of brownies!
.
But still pay attention to what you already cut.
.
Cut down the middle the other direction.
.
What's 4 x 2?
.
8.
.
Now, finally, we multiply the half of the half brownies.
.
What's 8 x 2?
.
16.
.
16 slices.
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We need to find out how many adults must the brand manager survey in order to be 90% confident that his estimate is within five percentage points of the true population percentage.
From the given data we know that our confidence level is 90%. From Standard Normal Table we know that the critical level at 90% confidence level is 1.645. In other words, .
We also know that E=5% or E=0.05
Also, since, is not given, we will assume that
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in the expression and that will be maximum only when
=0.5. (For any other value of
, we will get a value less than 0.25. For example if,
is 0.4, then
and thus,
.).
We will now use the formula
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which can approximated to n=271.
So, the brand manager needs a sample size of 271