
Elementary Math Fractions, Percentages, Word Problems, Equations, Inequations, Factorization, Expansion 
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September 15th, 2018, 06:01 AM  #1 
Member Joined: Sep 2018 From: Japan Posts: 35 Thanks: 2  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. 
September 15th, 2018, 08:35 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 21,132 Thanks: 2340 
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? 
September 15th, 2018, 10:54 AM  #3 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1039  
September 15th, 2018, 12:08 PM  #4 
Global Moderator Joined: Dec 2006 Posts: 21,132 Thanks: 2340 
That wouldn't work unless something else is changed.

September 15th, 2018, 03:36 PM  #5 
Member Joined: Sep 2018 From: Japan Posts: 35 Thanks: 2 
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. 
September 15th, 2018, 04:44 PM  #6 
Member Joined: Sep 2018 From: Japan Posts: 35 Thanks: 2 
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. 
September 16th, 2018, 10:43 AM  #7 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,597 Thanks: 1039 
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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cost, gift, splitting 
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