SOLUTION: the average of four numbers is 638.4 the first four numbers are 216 159.8 and 301.25 Find the fourth number.

Algebra ->  Average -> SOLUTION: the average of four numbers is 638.4 the first four numbers are 216 159.8 and 301.25 Find the fourth number.      Log On


   

Question 163277: the average of four numbers is 638.4 the first four numbers are 216 159.8 and 301.25 Find the fourth number.
Found 2 solutions by edjones, orca:
Answer by edjones(8007) About Me  (Show Source):
You can put this solution on YOUR website!
216+159.8+301.25+x=638.4*4
677.05+x=2553.6
x=2553.6-677.05
x=1876.55
.
Ed

Answer by orca(409) About Me  (Show Source):
You can put this solution on YOUR website!
Let the fourth number be x.
Then the average of the four number can be expressed as:
%28216+%2B+159.8+%2B+301.25+%2B+x%29%2F4
As the average is 638.4, we have
%28216+%2B+159.8+%2B+301.25+%2B+x%29%2F4=638.4
Solving the equation for x, we obtain
%28677.05+%2B+x%29%2F4=638.4
677.05+%2B+x=2553.6 (multiply both sides by 4)
x=1876.55