Tough and Tricky questions: Percents.
Over the course of a year, a certain microbrewery increased its beer output by 20 percent. At the same time, it decreased its total working hours by 30 percent. By what percent did this factory increase its output per hour? Choose the correct choice from the following: A) 171.4 B) 171.5 C) 171.6 D) 171.7 E) none of the above

Rationale: lets assume the initial production was 100 litres of beer for 100 hr . with the 20 % increase the total amount of beer production will be 120 litres and with 30 % decrease in total hours will be reduced to 70 hr . 100 hr - - - - > 100 lts 1 hr - - - - - > 1 lts 70 hr - - - - - > 120 lts 1 hr - - - - - > 1.714 lts total increase in production for 1 hr = 171.4 % answer a
Answer: A