The SUMPRODUCT$()$ Function $F_S$ is a highly useful function in Excel. It returns the sums of the products of corresponding cell ranges of the same size.

In our class, we often apply the SUMPRODUCT$()$ function to quickly calculate weighted averages, weighted totals, or expected values for tables of values in Excel.

E$.$g$.$ If you want to compute $100**5+200**8$ you could use $=$SUMPRODUCT $\{100,200\},\{5,8\}$

Relative, Absolute and Mixed Cell References $$ are also an important feature in Excel.

Understanding of absolute vs$.$ relative references can save you much time by copying formulas instead of manually entering them multiple times over.

We often use absolute and relative references in functions such as $=$SUMPRODUCT$(),=$SUM$(),$ and $=$AVERAGE$()$ to repeat those calculations many times quickly by simply copying the formula.

RELATIVE cell references are the default in Excel.

When a formula is copied to a new cell, the references in the formula change $-$ cells in the formula move by the corresponding number of rows or columns that the formula was moved.

Absolute references allow you to "lock" or "freeze" a given cell reference such that it does not change when copied.