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# The price of a certain commodity increased at a rate of x%

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CEO
Joined: 21 Jan 2007
Posts: 2739
Location: New York City
The price of a certain commodity increased at a rate of x% [#permalink]

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27 Dec 2007, 07:54
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The price of a certain commodity increased at a rate of x% each year between 2000 and 2004. If the price was M dollars in 2001 and N in 2003, what was the price in terms of M and N?

sqrt(MN)
N * sqrt(N/M)
N * sqrtM
N* M/sqrtN
N * M^(3/2)

Can someone show me the approach? not sure where to start
CEO
Joined: 21 Jan 2007
Posts: 2739
Location: New York City

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27 Dec 2007, 08:13
alright, i'm a little further along in the answer now.

why is year 2003
N = M* (1 + x/100)^2
and not
N = [M* (1 + x/100)]^2
Manager
Joined: 21 May 2007
Posts: 120
Re: percentage increase - algebra [#permalink]

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27 Dec 2007, 09:07
bmwhype2 wrote:
The price of a certain commodity increased at a rate of x% each year between 2000 and 2004. If the price was M dollars in 2001 and N in 2003, what was the price in terms of M and N?

sqrt(MN)
N * sqrt(N/M)
N * sqrtM
N* M/sqrtN
N * M^(3/2)

Can someone show me the approach? not sure where to start

Whats the question? which year's price you want to know?
Year 2000 - A
Year 2004 - B

Approach:
Let X be the price in 2000. r be the rate of interest. Then, the price in subsequent years is:
X(1+r/100), X(1+r/100)^2, X(1+r/100)^3,
This can be written as: Xq, Xq^2, Xq^3......
This is a Geometric sequence.
You know the 2nd and 4th term. You can find the common ratio and then the first term.
From this, you can find any term.

Hope that helps!
Re: percentage increase - algebra   [#permalink] 27 Dec 2007, 09:07
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