SAT Math Multiple Choice Practice Question 427: Answer and Explanation

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Question: 427

10. At the beginning of 1999, the population of Rockville was 204,000 and the population of Springfield was 216,000. If the population of each city increased by exactly 20% in 1999, how many more people lived in Springfield than in Rockville at the end of 1999 ?

A. 2,400
B. 10,000
C. 12,000
D. 14,400
E. 43,200

Correct Answer: D

Explanation:

D Take out your calculator:

216,000 + 20% of 216,000 = 259,200
204,000 + 20% of 204,000 = 244,800
259,200 – 244,800 = 14,400

Another route to the answer is to take the difference immediately (216,000 – 204,000 = 12,000) and then increase that by 20%.

Watch out for partial answers. E is 20% of Springfield's population, and A is the difference between 20% of Springfield's population and 20% of Rockville's population.

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