Given:
Number of mice and frequency
Mean = 7
To find:
The value of x.
Solution:
Number of mice = X
Frequency = Y
XY = Multiply X and Y values.
X Y XY
5 4 20
6 13 78
7 16 112
8 x 8x
9 6 54
Sum of Y = 4 + 13 + 16 + x + 6
= 39 + x
Sum of XY = 20 + 78 + 112 + 8x + 54
= 8x + 264
Mean formula:
[tex]$Mean = \frac{\Sigma XY }{\Sigma Y}[/tex]
[tex]$7=\frac{8x+264}{39+x}[/tex]
Do cross multiplication.
[tex]7(39+x)=(8x+264)[/tex]
[tex]273+7x=8x+264[/tex]
Subtract 264 from both sides, we get
[tex]9+7x=8x[/tex]
Subtract 7x from both sides, we get
[tex]9=x[/tex]
The value of x is 9.
