The Brookfield girl scouts sold 90 boxes of cookies on their first day which averaged 30% more than the other local area teams. Increasing their effort, by the end of the second day their sales increased their average to be 50% more than the other teams. How many boxes of cookies must the girls have out sold by to have attained this average? Choose the correct choice from the following answers:
A) 12 B) 50 C) 20 D) 36 E) 15
Explanation: First, set the information into algebraic phrases, set that information into an equation, then solve.   Number of boxes sold the first day @ 30% more: 30% * 90=27   Increasing their effort on the second day average increased to 50%. (Let x represent the unknown amount of additional cookies sold to solve the equation.) Therefore, the total boxes sold by the girls is 90+x, and the total number of boxes increased in 27+x. This gives the equation as: 50%*(90+x)=27+x   Solve: Let's get rid of the percent sign   50/100*(90+x)=27+x   1/2 *(90+x)=27+x   Get rid of the fraction:   2[1/2 * (90+x)]=2(27+x)   1 * (90+x) =54+2x   90+x =54+2x   (90-54)+x = (54-54)+2x   36+x/x = 2x/x   36 = x   Answer: 36
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The Brookfield girl scouts sold 90 boxes of cookies on their first day which averaged 30% more than the other local area teams. Increasing their effort, by the end of the second day their sales increased their average to be 50% more than the other teams. How many boxes of cookies must the girls have out sold by to have attained this average?