given an average of 90
and the following as her test: 88, 94, 81, 96 and 82
recall that we were told that she has one test left
so lets make X the one test left
therefore, taking average:
88 + 94 + 81 + 96 + 82 + X/6 = 90
lets cross multiply
88 + 94 + 81 + 96 + 82 + X = 90 x 6
adding up the left hand side and multiplying the right hand side
441 + X = 540
collecting like terms,
X = 540 - 441
X = 99
therefore the grade that hse must earn on her last test for to qualify is 99
