SOLUTION: the average of 15 men in a boat is increased by 3 kg when one of the crew who weights 40kg, is replaced by someone else. the weight of the new man is

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Question 791934: the average of 15 men in a boat is increased by 3 kg when one of the crew who weights 40kg, is replaced by someone else. the weight of the new man is
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
the average of 15 men in a boat is increased by 3 kg when one of the crew who weights 40kg, is replaced by someone else.
the weight of the new man is:
:
Let k = the average weight of the 1st 14 guys
Let A = the original average of the 15 guys
then
(A+3) = the average when one guy is replaced
let x = the weight of the new guy.
:
Equation for the original crew
%2814k%2B40%29%2F15 = A
14k + 40 = 15A
:
Equation when one guy is replaced
%2814k%2Bx%29%2F15 = A + 3
14k + x = 15(A+3)
14k + x = 15A + 45
14k + x - 45 = 15A
:
15A = 15A so we can write it
14k + x - 45 = 14k + 40
subtract 14k from both side
x - 45 = 40
x = 40 + 45
x = 85 kg, weight of the new guy, a big dude!