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May 19, 2013

Posted by danny on Saturday, January 30, 2010 at 6:51pm.

Find the value of x so that the mean of {5x, 3/2x, x+9, -x} is -1.

a. 2
b. 1/2
c. -1/2
d. -2

My answer is d. Is it correct.

• adv. math - Reiny, Saturday, January 30, 2010 at 8:07pm

then (5x + (3/2)x + x+9 - x)/5 = -1
5x + (3/2)x + x+9 - x = -5
5x + (3/2)x + 9 = -5
10x + 3x + 18 = -10
13x = -28
x = -28/13

(5(-28/13) + (3/2)(-28/13) + 9 = -5

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