The price of electricity was first increased by 10 percent and then the new price was decreased by 25 percent. The final price was what percent of the initial price?
A. 78% B. 80% C. 82.5 D. 85% E. 87.5%
SOLUTION
Let the original price = a
Since the price increased by 10 percent,
Then the new price = (10 + 100) % of a = 110 ×a = 110%a
Since the new price later decreased by 25%,
Then the final price = (100- 25) % ×110%a = 75% ×110%=8250/10000
=82.50%ans (C)

2. Lucy noted that she is both the 12th tallest and the 12th shortest student in her class. If everyone in the class is a different height, how many students are in the class?
A. 22 B. 23 C. 24. D. 25 E. 34
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