SOLUTION: Julie cashed a paycheck and repaid her brother $10 that she had borrowed from him. She then spent $30 on fuel for her car and half of the remaining money on a new tent for camping.

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Question 1204068: Julie cashed a paycheck and repaid her brother $10 that she had borrowed from him. She then spent $30 on fuel for her car and half of the remaining money on a new tent for camping. She bought a pair of running shoes for $29.45 and had $17.75 left. How much did Julie receive when she cashed her paycheck?
Found 3 solutions by math_tutor2020, MathTherapy, ikleyn:
Answer by math_tutor2020(3817)   (Show Source): You can put this solution on YOUR website!

x = her paycheck amount
x-10 = what she has left over after repaying her brother
x-10-30 = x-40 = left over amount after buying fuel

(1/2)(x-40) = 0.5x-20 = amount she has left after buying the tent

0.5x-20-29.45 = 0.5x-49.45 = amount she has left after buying the shoes

Set this equal to the stated value 17.75 so we can solve for x.
0.5x-49.45 = 17.75
0.5x = 17.75+49.45
0.5x = 67.20
2*0.5x = 2*67.20
x = $134.40 is the answer.

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Checking the answer:

start = $134.40
repays brother = $134.40 - $10 = $124.40 left over
buys fuel = $124.40 - $30 = $94.40 left over
buys tent = (1/2)*($94.40) = $47.20 left over
buys shoes = $47.20 - $29.45 = $17.75 is what she'll have left over after purchasing all the items mentioned, and repaying her brother.
Answer is confirmed.


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Another approach

She ended up with $17.75
Add on the price of the shoes to rewind the clock so she gets that money back.
17.75+29.45 = 47.20
Before buying the shoes, she would have $47.20

Double this to get $94.40 when we rewind the clock further back. This is the amount she would have just before buying the tent.
Then add on $30 to rewind further to get $124.40 to represent what she would have just before buying fuel.

Lastly, she'll take the $10 from her brother when rewinding the clock all the way back to the start point.
$124.40+$10 = $134.40
Basically we follow the "check" section shown above, but do so in reverse.
Any time we have a subtraction, the inverse would be addition. The inverse of halving is doubling.
This rewinding action is basically how we solve equations.

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Answer: $134.40

Answer by MathTherapy(10552)   (Show Source): You can put this solution on YOUR website!
Julie cashed a paycheck and repaid her brother $10 that she had borrowed from him. She then spent $30 on fuel for her car and half of the remaining money on a new tent for camping. She bought a pair of running shoes for $29.45 and had $17.75 left. How much did Julie receive when she cashed her paycheck?

Sometimes it's easier to work BACKWARDS, from the final remainder to the initial mount. 
In this case though, I'll go forward. 

Let paycheck amount be P
After repaying her brother $10 and buying fuel for $30, she had P - 10 - 30, or P - 40 remaining
After paying  of remainder for a tent, she had , remaining
After buying the shoes for $29.45, she had a FINAL remainder of 
As her FINAL remainder was $17.75, we get: 
                                                  
                                                   P - 40 = 94.4 ----- Cross-multiplying
                                         Paycheck, or P = 94.4 + 40 = $134.40

Answer by ikleyn(52788)   (Show Source): You can put this solution on YOUR website!
.
Julie cashed a paycheck and repaid her brother $10 that she had borrowed from him.
She then spent $30 on fuel for her car and half of the remaining money on a new tent for camping.
She bought a pair of running shoes for $29.45 and had $17.75 left.
How much did Julie receive when she cashed her paycheck?
~~~~~~~~~~~~~~~~~~~


        Tutor @MathTherapy mentioned very productive idea on use the backward method for this problem.
        In this my post I will show how effectively this idea works.


So, let's stsart from the end.


Before Julie bought a pait of running choes, she had 17.75 + 29.45 = 47.20 dollars.

This amount was the "second half" of her "remaining" money - so, the "remaining" money amount 
was 2*47.20 = 94.40 dollars .


Hence, her paycheck was $ 94.40  PLUS  $30  PLUS  $30,  i.e.  94.40 + 10 + 30 = 134.40 dollars.


ANSWER.  The paycheck was $134.40.

Solved.

The backward method in this problem works  SO  EFFECTIVELY,
that the problem can be solved  MENTALLY  in couple of lines without using equations.



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