Robert's salary was increased by 50% and subsequently decreased by 10%. how much percentage does he gain?	Pick one:
A) 15 %  B) 20 %  C) 10 %  D) 25 %  E) 30 %

Rationale: let original salary be $ 100 increased salary = 10 % of ( 150 % of $ 100 ) = ( 10 / 100 ) * ( 150 / 100 ) * 100 = $ 15 increase = 15 % correct option is a
Answer: A