You are given a math word problem and you are supposed to make use of mathematical concepts like probability, combinatorics, linear equations, sequences/series, or simple operators like addition, subtraction, division, or multiplication to answer the given question. Choose the best option from the 5 given options and report that option.

Q: Question: The average salary per head of the entire staff of an office including the officers and clerks is Rs.90. The average salary of officers is Rs.500 and that of the clerks is Rs.84. If the number of officers is 2, find the number of officers in the office?

 Option A: 620

 Option B: 720

 Option C: 820

 Option D: 920

 Option E: 1020

A: Option C
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Q: Question: A reduction of 20% in the price of salt enables a lady to obtain 10kgs more for Rs.100, find the original price per kg?

 Option A: Rs.2.9

 Option B: Rs.2.1

 Option C: Rs.2.5

 Option D: Rs.2.2

 Option E: Rs.2.7

A: Option C
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Q: Question: One pipe can fill a pool three times faster than a second pipe. When both pipes are opened, they fill the pool in seven hours. How long would it take to fill the pool if only the slower pipe is used?

 Option A: 10 hr

 Option B: 12 hr

 Option C: 15 hr

 Option D: 20 hr

 Option E: 28 hr

A:
Option E
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