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# $4800 becomes$6000 in 4 years at a certain rate of compound interest.

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Manager
Joined: 25 Dec 2018
Posts: 130
Location: India
Concentration: General Management, Finance
GMAT 1: 590 Q48 V23
GPA: 3.4
WE: Engineering (Consulting)
$4800 becomes$6000 in 4 years at a certain rate of compound interest.  [#permalink]

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06 Mar 2019, 01:19
3
00:00

Difficulty:

25% (medium)

Question Stats:

85% (02:22) correct 15% (02:12) wrong based on 13 sessions

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$4800 becomes$6000 in 4 years at a certain rate of compound interest. What would have been the amount after 12 years?

A) $9500 B)$9375
C) $9250 D)$9775
E) $9250 Math Expert Joined: 02 Aug 2009 Posts: 7422 Re:$4800 becomes $6000 in 4 years at a certain rate of compound interest. [#permalink] ### Show Tags 07 Mar 2019, 07:42 mangamma wrote:$4800 becomes $6000 in 4 years at a certain rate of compound interest. What would have been the amount after 12 years? A)$9500
B) $9375 C)$9250
D) $9775 E)$9250

Calculation of r and then finding amount after 12 years will be calculation intensive.
A very innovative way to avoid cumbersome calculation would be ..
The formula for CI is Amount = P$$(1+\frac{r}{100})^t$$.... 6000 = 4800$$(1+\frac{r}{100})^4..........(1+\frac{r}{100})^4=\frac{6000}{4800}.$$..
we are looking for 4800$$(1+\frac{r}{100})^12$$=4800$$((1+\frac{r}{100})^4)^3$$=4800$$(\frac{6000}{4800})^3=4800*\frac{5*5*5}{4*4*4}=75*125=9375$$

B
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2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html
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Re: $4800 becomes$6000 in 4 years at a certain rate of compound interest.   [#permalink] 07 Mar 2019, 07:42
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