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Percentages

by teejaycrown » Fri Nov 02, 2012 10:23 pm
What was the % increase in the population of city k from 1980 to 1990

1. in 1970 the population of city k was 160,000
2. In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970
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by Anurag@Gurome » Fri Nov 02, 2012 11:28 pm
teejaycrown wrote:What was the % increase in the population of city k from 1980 to 1990

1. in 1970 the population of city k was 160,000
2. In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970
(1) In 1970 the population of city k was 160,000. But this alone is NOT sufficient to find the desired percent increase in population.

(2) In 1980, the population of city k was 20 % greater than it was in 1970 and in 1990 the population of city k was 30% greater than it was in 1970.
Let us assume that population in 1970 = P.
Then in 1980 population = P + 0.20P = 1.2P
In 1990, population = P + 0.30P = 1.3P

So, percent increase from 1980 to 1990 = (1.3P - 1.2P)100/1.2P; SUFFICIENT.

The correct answer is B.
Anurag Mairal, Ph.D., MBA
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