Tonya D.

asked • 07/05/15

Word Problem Equation

Mary had some cookies. She gave 2/9 of them to Matthew and ate 1/3 of them. She had 8 cookies left. How many did she have at forst?

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Michael J. answered • 07/06/15

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Applying SImple Math to Everyday Life Activities

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Let x = the amount she started with.
 
Since she gave away a fraction of some cookies, then ate a fraction of the cookies she had left after that, this tells us to subtract.  The end result is 8.
 
 
x - (2/9)x - (1/3)(x - (2/9)x) = 8
 
 
Solve for x.
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Jayden H.

The equation above is written as though Mary first gives 2/9 of the amount she had first to Matthew and then eats 1/3 of the amount left after giving some to Matthew and is finally left with 8 cookies. Solving for x gives a value involving broken cookies.

If we think of the question instead as each decrease in amount of cookies being measured from the initial amount the equation becomes:
 
x - (2/9)x-(1/3)x = 8
 
the value of x is a total of whole cookies.  
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07/06/15

Andrew M.

That's the problem with ambiguous wording, which we run into a lot.  I'm fairly certain the teacher or text expects you to assume that 2/9 of the original amount was given away and 1/3 of the original amount was eaten, leaving 8 ...  so you would use Jayden H's equation...  the final answer then is she originally had 18 cookies.
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07/06/15

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