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# If P=S(1+r/100)^n where P is the amount from investment, S is principa

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Math Revolution GMAT Instructor
Joined: 16 Aug 2015
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If P=S(1+r/100)^n where P is the amount from investment, S is principa  [#permalink]

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30 Mar 2016, 23:27
00:00

Difficulty:

55% (hard)

Question Stats:

58% (01:37) correct 42% (01:32) wrong based on 72 sessions

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If P=S(1+r/100)^n where P is the amount from investment, S is principal, and r is a compound interest rate after n years, by what percent the amount from investment increases between after n years and after n+5 years?

1) n=10
2) r=10

* A solution will be posted in two days.

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Marshall & McDonough Moderator
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Re: If P=S(1+r/100)^n where P is the amount from investment, S is principa  [#permalink]

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31 Mar 2016, 00:04
Percentage increase = ((Final Value - Initial Value)/(Initial Value))*100 = ((Final Value/Initial Value) - 1)*100

Final value/Initial value = (1 + r/100)^(n+5)/(1 + r/100)^n = (1 + r/100)^(n + 5 - n) = (1 + r/100)^5

Answer is dependent on the value of 'r'.

St2 is sufficient.

Math Revolution GMAT Instructor
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Re: If P=S(1+r/100)^n where P is the amount from investment, S is principa  [#permalink]

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03 Apr 2016, 02:50
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

If P=S(1+r/100)^n where P is the amount from investment, S is principal, and r is a compound interest rate after n years, by what percent the amount from investment increases between after n years and after n+5 years?

1) n=10
2) r=10

When you modify the original condition and the question, you only need to figure out r from
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Re: If P=S(1+r/100)^n where P is the amount from investment, S is principa  [#permalink]

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17 Feb 2019, 00:20
Here, interest refers to compound or simple?? If compound, then I believe the interest will vary as per time also..
Re: If P=S(1+r/100)^n where P is the amount from investment, S is principa   [#permalink] 17 Feb 2019, 00:20
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