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Writing Proportions

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    I have three word problems in this video.
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    What I want to do in this video is not solve the word problems,
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    but setup the equation that we could solve to get the answer to the word problem.
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    What we are essentially going to do is setup the proportionality for the word problems.
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    So In this 1st problem
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    we have 9 markers cost $11.50. And then they ask:
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    How much will 7 markers cost.
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    Now, let's just set X to be equal to our answer, where X is equal to the cost of 7 markers.
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    The way to solve a problem like this is to setup two
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    ratios and set them equal to each other.
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    So you could say that the ratio of 9 markers
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    to the cost of 9 markers; 9/ 11.50 = 7/ X
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    This is a completely valid proportion here.
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    You could solve this to figure out how much those
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    7 markers will cost.
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    You could have 11.50/9 = X/7 .This is also a valid ratio.
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    You could also think about ratios in other ways
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    You could say, that the ratio of 9 markers to 7 markers,
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    is going to be same as the ratio of their cost
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    9/7 = 11.5/X or 7/9 = X/11.5
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    So all of these would be valid proportion.
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    Sp let's do this problem now. 7 aples cost $5.
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    How much can I buy with $8.
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    How many apples - let's call that X. We need to solve for X
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    So we have the ratio between number
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    of apples and cost of the apples - 7/5= X/8
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    In this first situation the unknown was cost, in this example
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    the unknown is number of apples.We can do all the different
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    scenarios as above. we could say 7/X = 5/8
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    Now lets do the last one. We have a cake recipe for
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    5 people requires 2 eggs. How many eggs? So we want to know how many eggs?
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    We will call how many eggs, which we
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    need to find out as X, we can call it anything Y,A,B,C anything.
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    So you could say the ratio of people to eggs is constant.
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    We have 5 people for 2 eggs - 5/2 = 15/X
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    Or you could say the ratio between 5/15 = 2/X
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    All of these we setup the proportion and we can
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    solve for X and get the answer.
Title:
Writing Proportions
Description:

Setting up proportions to solve a word problem

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Video Language:
English
Duration:
05:51