Homework Help: math

Posted by felicia on Saturday, June 2, 2012 at 8:45pm.

Tim wants his mean (average) quiz score in history class to be 90. His first 3 quiz scores were 86, 92, and 94. What score should he make on the 4th quiz in order to have a mean (average) quiz score of exactly 90?

I really need the answer ! PLZ PLZ PLZ ! cant figure it outtt !!!! -___-

math - felicia, Saturday, June 2, 2012 at 8:54pm
Nvmd yo ! I got it !
math - Bosnian, Saturday, June 2, 2012 at 10:55pm
x1 + x2 + x3 = 86 + 92 + 94 = 272

( x1 + x2 + x3 + x4 ) / 4 = 90

( 272 + x4 ) / 4 = 90 Multiply both sides by 4

272 + x4 = 90 * 4

272 + x4 = 360

x4 = 360 - 272 = 88

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