<PRE><B>Question 1149800</B>
let x = the total value
let n = the number of elements that make up the total.


the average mass at first was 42.
formula for that is x/n = 42


additional person weighing 70 kg is added to the group.
the average mass becomes 46.
formula for that is (x+70)/(n+1) = 46


solve for x in the first equation to get x = 42*n
replace x in the second equation to get (42*n+70)/(n+1) = 46
multiply both sides of this equation by (n+1) to get:
(42*n+70) = 46*(n+1)
simplify to get 42*n+70 = 46*n+46
subtract 42*n from both sides of the equation and subtract 46 from both sides of the equation to get:
70-46 = 46*n-42*n
simplify to get:
24 = 4*n
solve for n to get n = 6


x/n = 42 becomes x/6 = 42
solve for x to get x = 252


(x+70)/(n+1) = 46 becomes (252+70)/(6+1) = 46 which becomes 322/7 = 46 which becomes 46 = 46 which is true.


your solution is that there were 6 people in the group at first.


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