Question

Write the sigma notation mean formula for the second semester beginning in February and determine that semester average rounded to the nearest dollar.

Answer 1

We want to write the formula to evaluate the average for the second semester, which means we will use Feb, Mar, Apr, and May to evaluate it, they are

`x_6,x_7,x_8,x_9`

Writing the formula:

`\mu=(x_6+x_7+x_8+x_9)/(4)=\frac{\sum_{n\mathop{=}6}^9x_n}{4}`

Or

`\mu=(1)/(4)\sum_{n\mathop{=}6}^9x_n`

Which is

`\mu=(1)/(4)\sum_{n\mathop{=}6}^9x_n=(80+78+78+67)/(4)=(303)/(4)=\$75.75`

Rounding it to the nearest dollar:

`\mu=\$76`

The average cable bill is $76