SOLUTION: 7. Frank bought supplies for school. In the first store, he spent half of his money plus $10. In the second store, he spent half of what he had left, plus $10. In the third stor

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Question 1090359: 7. Frank bought supplies for school. In the first store, he spent half of his money plus $10. In the second store, he spent half of what he had left, plus $10. In the third store, he spent 80% of what he had left. He came home with $5. How much did he start out with?
Answer by jorel1380(3719) About Me  (Show Source):
You can put this solution on YOUR website!
Let n be the amount Frank started with. Then, after each store, he would have:
1st store:n/2 -10
2nd store:1/2(n/2 -10) -10
3rd store:.2((1/2(n/2 -10) -10))
So: .2((1/2((n/2 -10) -10))=5
Then, solve for n
You can also work backwards. For example, Frank ends with $5. Since, in the third store, he spent 80% of what he had left after the second store, he would have 5/.2, or $25. Then, add $10 and multiply by 2 to get $70, etc..
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