Given a math problem with context and a question and 5 answer choices, the task is to provide the correct answer choice based on the problem. You must choose one of the given answer choices by letter: a, b, c, d, or e; anything else is invalid.

Q: Problem: by selling 15 pencils for a rupee a man loses 20 %. how many for a rupee should he sell in order to gain 20 % ?
Options: a. 8, b. 7, c. 6, d. 4, e. 10

A: e
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Q: Problem: for any positive integer n, the sum of the first n positive integers equals n ( n + 1 ) / 2. what is the sum of all the integers between 100 and 200 ?
Options: a. 4545, b. 5050, c. 6525, d. 4352, e. 4652

A: b
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Q: Problem: the area of a square land is a square feet and the perimeter is p feet. if 5 a = 10 p + 45, what is the perimeter of the land, in feet ?
Options: ['a. 18', 'b. 56', 'c. 40', 'd. 36', 'e. 64']

A:
d
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