If you copy the formula you quoted into another row, or fill it down using Ctrl+D, it will automatically change the reference to the row you are copying/filling to. This is called a “relative reference”. If you use the formula `=PRODUCT($A$1:$B$1)`

, this is called an “absolute reference”, which will not change if copied elsewhere.

You can also use the following formula in any row:

`=A:A*B:B`

which will return the product of the two values in the row the formula is invoked.