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Marty has a coin collection, which consists of only New World and Old

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Marty has a coin collection, which consists of only New World and Old [#permalink]

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New post 16 Aug 2017, 01:59
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A
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C
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  15% (low)

Question Stats:

78% (01:32) correct 22% (01:19) wrong based on 68 sessions

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Marty has a coin collection, which consists of only New World and Old World coins, in a ratio of 3:1. Marty’s friend Kyle swaps 28 of his Old World Coins for 28 of Martin’s New World coins. If Marty now has as many Old World coins as he does New World coins, how many coins did Marty originally have in his collection?

(A) 28

(B) 84

(C) 112

(D) 130

(E) 390

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Re: Marty has a coin collection, which consists of only New World and Old [#permalink]

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New post 16 Aug 2017, 02:12
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3x-28/x+28=1; 2x=56; x=28; 4x=112
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Re: Marty has a coin collection, which consists of only New World and Old [#permalink]

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New post 16 Aug 2017, 04:39
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\(\frac{Nw}{Ow}\)=3=> Nw= 3Ow

After the swap
Nw-28= Ow+28
=>3 Ow-28= Ow+28
=>2Ow= 56
=>Ow= 28
Nw=3ow= 28*3= 84

Total coins originally = 84+28=112

Ans- C
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Marty has a coin collection, which consists of only New World and Old [#permalink]

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New post 16 Aug 2017, 05:47
Old Ratio (New Coins:Old Coins) : 3:1
Total Coins = 3n + n = 4n

New Ratio: 1:1
New Arrange: (3n-28 / n+28) = (1/1)

Cross Multiply:
3n-28=n+28
2n = 56
n = 28

So, 4n = 112
Answer C
Marty has a coin collection, which consists of only New World and Old   [#permalink] 16 Aug 2017, 05:47
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