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.
--------
Question: Problem: a fraudulent dairy guy declares to market his dairy at price range but he combined it with water and therefore benefits 25 %. the percentage of water in the combination is :
Options: a. 20 %, b. 30 %, c. 50 %, d. 35 %, e. 60 %

Answer: a


Question: Problem: if the simple interest on a certain sum of money for 6 years is one – fifth of the sum, then the rate of interest per annum is
Options: a. 3.3 %, b. 7.2 %, c. 6.1 %, d. 5.0 %, e. 3.1 %

Answer: a


Question: Problem: a tank is filled in 10 hours by 3 pipes a, b and c. the pipe c is twice as fast as b and b is twice as fast as a. how much time will pipe a alone take to fill the tank ?
Options: a. 70 hours, b. 30 hours, c. 35 hours, d. 50 hours, e. 60 hours

Answer:
a