The population of state X increases by 10 percent every 10 y

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[Math Revolution GMAT math practice question]

The population of state X increases by 10 percent every 10 years. If the population in 1990 was P million, how much larger is the population in 2010 than the population in 1990?

A. 0.1*P
B. 1.1*P
C. 0.01*P
D. 0.11*P
E. 0.21*P

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by Max@Math Revolution » Sun Jul 29, 2018 5:21 pm
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The population in 2010 is (1.1)^2P and the difference between the populations in 2010 and in 1990 is (1.1)^2P - P = ((1.1)^2 - 1)P = (1.1+1)(1.1-1)P = 2.1*0.1P = 0.21P.
Therefore, the answer is E.
Answer: E

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by Jeff@TargetTestPrep » Mon Jul 30, 2018 10:48 am
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

The population of state X increases by 10 percent every 10 years. If the population in 1990 was P million, how much larger is the population in 2010 than the population in 1990?

A. 0.1*P
B. 1.1*P
C. 0.01*P
D. 0.11*P
E. 0.21*P

If the population in 1990 was P million, then the population in 2000 was P x 1.1 = 1.1P million, and the population in 2010 was 1.1P x 1.1 = 1.21P million. Therefore, the population in 2010 was 1.21P - P = 0.21P larger than the population in 1990.

Answer: E

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