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September 15th, 2018, 06:01 AM   #1
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Splitting the cost of a gift.

Devi, Sam and Nora shared the cost of a gift for their friend. The amount Devi and Sam paid was 3/10 of the cost and the amount Sam and Nora paid was 7/10 of the cost. Devi paid 5.85 dollars and Nora paid 13.80 dollars more than Devi. How much did Sam pay?

My work:

How much Devi paid = D
How much Sam paid = S
How much Nora paid = N
Total money the spent = C

We Know D + S = 3/10C

We Know S + N = 7/10C

We know D spent 5.85. So, D = 5.85

We know N spend 13.80 more than D. So N = D + 13.80


Then I did elimination:

19.65 + S = 7/10C
- 5.85 + S = 3/10C
------------------------------
= 13.80 = 4/10C

So, C =34.50.


We are looking for how much Sam paid, so then I did this below. And I'm
going to use this: D + S = 3/10C

5.85 + Sam = 3/10(34.5)

Sam = 4.50


I'm not sure whether I did the math correct.

Last edited by skipjack; September 15th, 2018 at 07:45 AM.
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September 15th, 2018, 08:35 AM   #2
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The question gives D + S = 3/10C and S + N = 7/10C.

Adding those equations gives D + 2S + N = C, which implies that another person (or other persons combined) also shared the cost and paid the same amount as Sam.

All of your work was correct, but are you sure the problem was stated correctly?
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September 15th, 2018, 10:54 AM   #3
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Quote:
Originally Posted by xoritos View Post
Devi paid 5.85 dollars and Nora paid 13.80 dollars more than Devi.
Nora probably paid 13.80 more than Sam, not Devi,
else the wording would be Nora paid 19.65
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September 15th, 2018, 12:08 PM   #4
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That wouldn't work unless something else is changed.
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September 15th, 2018, 03:36 PM   #5
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Thank you for all the response.

I double checked the wording of the question, it's 100% correct.

"Devi paid %5.85 and Nora paid "$13.80" more than Devi"

It seems like I did the problem incorrect, but I'm not seeing what I did wrong?

Last edited by xoritos; September 15th, 2018 at 03:39 PM.
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September 15th, 2018, 04:44 PM   #6
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Because 5.85 + 4.50 + 19.65= 30. It's just a bad question. Thank you everyone for clearing it up.

Last edited by skipjack; September 16th, 2018 at 03:12 AM.
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September 16th, 2018, 10:43 AM   #7
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Try this similar one:

A, B and C shared the cost of a gift for their friend.
A and B together paid 7/9 of the cost.
A paid 120 and C paid 60.
How much did B pay?
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