SOLUTION: the average of 45 numbers is 9.the average of first 20 is 10 and the average of the last 24 numbers is 8 .find 21st number?

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Question 628372: the average of 45 numbers is 9.the average of first 20 is 10 and the average of the last 24 numbers is 8 .find 21st number?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
the average of 45 numbers is 9. the average of first 20 is 10
and the average of the last 24 numbers is 8
.find 21st number
:
Let x = the 21st number
:
%2820%2810%29%2B24%288%29%2Bx%29%2F45 = 9
:
%28200%2B192%2Bx%29%2F45 = 9
:
%28392%2Bx%29%2F45 = 9
mult both sides by 45
392 + x = 45(9)
x = 405 - 392
x = 13