Question

Theresa earned scores of 88 points, 84 points, 88 points, and 91 points on four tests. What is the lowest score she can get on the fifth test and still finish with an average score of 90 points?
96 points
97 points
98 points
99 points

Answer 1

So u will do 88+84=172+88=260+91=351 and that is all four tests added up now u have to divide the answer by 4 because it was four tests averages
351/4=87.75 wich is aproxamately 88 
so with all four of them added wich is 351 u will add the answer choices so 351+96=447/5=89.4 wich is aproxamately 89
351+97=448/5=89.6 wich is aproxamately 90
351+98=449/5=89.8 wich is aproxamately 90
351+99=450/5=90
so i would say that 99 points is the one she needs to score because it isnt asking for aproxamately 
so it is 99 points

Answer 2

Find the lowest score for the average. Let that number = x

There are 5 tests in all

(88 + 84 + 88 + 91 + x)/5 = 90

First, multiply 5 to both sides

(88 + 84 + 88 + 91 + x)/5(5) = 90(5)

88 + 84 + 88 + 91 + x = 450

Next, Combine like terms

351 + x = 450

Next, isolate the x. Subtract 351 from both sides

351 (-351) + x = 450 (-351)

x = 450 - 351

x = 99

99 is your answer

hope this helps