Nesting functions in Excel allows you to perform complex calculations in a single formula. Here's how you can nest SUM with AVERAGE and COUNTIF:

Scenario: You have a dataset with product sales figures and want to calculate the average sales for products that sold more than 10 units.

Formula Breakdown:

```excel
=SUM(AVERAGEIFS(sales_range, condition_range, ">10"))
```

Explanation:

1. AVERAGEIFS: This function calculates the average of a range (sales_range) based on one or more conditions.
2. Condition_range: This specifies the cell range containing the data you want to apply the condition to (e.g., number of units sold).
3. ">10": This is the actual condition. It filters the sales_range to only include products with sales greater than 10.
4. SUM: The outer SUM function takes the average result from AVERAGEIFS and adds up those values.

Result:

This formula will return the total average sales for products that sold more than 10 units.

Nesting Variations:

* You can nest COUNTIF inside AVERAGEIFS to achieve more complex criteria. For example, `=SUM(AVERAGEIFS(sales_range, condition_range1, ">10", condition_range2, "Product A"))` would calculate the average sales for product A that sold more than 10 units.
* Remember, nesting functions can become complex. Use parentheses strategically to ensure the correct order of operations.

Tips:

* Ensure your ranges are correct and consistent throughout the nested functions.
* Use clear cell references or named ranges for better readability.
* Consider using helper columns for intermediate calculations if the formula gets too complex.

By nesting SUM with AVERAGE and COUNTIF, you can perform powerful conditional calculations within a single formula, saving time and effort in your Excel tasks.