1 ) Let's solve this problem, setting a proportion
50----------- 100%
90------------- x
Cross multiplying it
50x =9000 Divide both sides by 50
x= 180
2) Since the question wants the percent of the increase, and 90 is equivalent to 180% then we can subtract:
180% -100% = 80%
3) Then the percent of increase from 50 to 90 is 80%
