Anichka wrote:

In the first half of the 20th century, the population of a particular country increased by 200 percent. In the second half of the century, the population increased by 300 percent. What was the percent increase for the 20th century as a whole?

(A) 500%

(B) 600%

(C) 800%

(D) 1100%

(E) 1200%

Could you explain why the correct answer is (D)?

The question is from MBA Center GMAT Study Book.

Thank you!

Say initially population was 100.

What is 200% of 100? It is 200/100 * 100 = 200.

An increase of 200% means the new population became 100 + 200 = 300

What is 300% of 300? It is 300/100 * 300 = 900

An increase of 300% means the new population now is 300 + 900 = 1200

So from 100, the population increased to 1200 i.e. an increase of 1100.

1100 is what percent of 100?

1100 = x/100 * 100

i.e. it is 1100%

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Karishma

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