TRUNC is a worksheet function in Excel that allows you to truncate a number to a certain number of decimal places. It is useful when you want to round a number down to the nearest whole number or to a certain number of decimal places.

To use the TRUNC function, select the cell in which you want the result to appear and enter the following formula:

`=TRUNC(number, num_digits)`

where `number`

is the number that you want to truncate and `num_digits`

is the number of decimal places that you want to keep. For example, if `number`

is 12.345 and `num_digits`

is 2, the result will be 12.34.

You can also use the TRUNC function to round a number up or down to the nearest multiple of a certain number. To do this, enter a negative value for `num_digits`

. For example, if `number`

is 12.345 and `num_digits`

is -2, the result will be 12.35 (rounded up to the nearest multiple of 2).