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.

Question: A rectangular plot measuring 90 metres by 50 metres is to be enclosed by wire fencing. If the poles of the fence are kept 10 metres apart, how many poles will be needed ?

Option A: 28

Option B: 56

Option C: 57

Option D: 58

Option E: None of these
Option A

Question: 8 persons can build a wall 140m long in 42 days. In how many days can 30 persons complete a similar wall 100 m long?

Option A: 12

Option B: 10

Option C: 8

Option D: 6

Option E: 5
Option C

Question: A solution of X pounds of water and sugar is boiled until 20% of the water content evaporates. Originally s% of sugar was present in the solution. After evaporation, what percentage of the solution is sugar?

Option A: 100s/(1-s

Option B: 80s/(1-s

Option C: 75s/(1-s

Option D: 100s/(80-0.2s

Option E: 100s/(80+0.2s
Option E