Question

Sandra has 4 math tests this marking period. She recieved 90%, 87%, and 92% on the first 3. with is the minimal score she needs on her last test in order to average at least 90% in math class?

Answer 1

The minim she can get for a score is a 90%

Answer 2

Let the unknown score be x
(Sum of the scores)/(number of tests) = avg
(90+87+92+x)/4 = 90
(269+x)/4 = 90
269 + x = 90*4
269 + x = 360
x = 360-269 = 91

So Sandra needs a minimal score of 91% on her last test in order to average at least 90% in math class

I hope this helps :)