In the first half of the 20th century, the population of a

Question

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%

The question is from MBA Center GMAT Study Book.

KarishmaB · Answer

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%

ajdse22 · Answer

This question plays some tricks. It is important to keep track. 
We can start with any number since the answer choices are in percents. 
let that number be 100. In the first half this increases by 200%. A 200% percent increase means an increase of 200% * 100 = 200. The new number is 300. From here we need to increase by 300%. 
So the new increase is 3*100% *300 = 900. The final number by the end of 20th century is 900+300= 1200. From the start this represents a 
increase by (1200-100)/100 => 11 times . Expressing this in % means multiply this by 100 . This is 1100% increase

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In the first half of the 20th century, the population of a

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