Problem 1. Sam has Average of three marking periods M3 = 89. What grade he need in MP4 to get Final Average: Mf = 91

First, let’s make an equation

(M1 + M2 + M3 + M4)/4 = 91

Now let’s just assume that M1-3 all equal 89

(89 + 89 + 89 + M4)/4 = 91

(267 + M4)/4 = 91

Now let’s apply the multiply both sides by 4

267 + M4 = 364

And subtract 267 from both sides

M4 = 97

To check plug into the original equation:

(89 + 89 + 89 + 97)/4 = 91

Final Sam needs a 97 in M4