SOLUTION: the mean of a set of numbers is 120. if one number is increases by 300, the mean increases to 135. how many numbers are in the set?

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Question 359452: the mean of a set of numbers is 120. if one number is increases by 300, the mean increases to 135. how many numbers are in the set?
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
Let x=numbers in the set.
(120(x-1)+420)/x=135
(120x-120+420)/x=135
(120x+300)/x=135
120x+300=135x
15x=300
x=20 numbers in the set.
.
Ed