What are the mathematical functions?

Count;

Is a calculation of the column of numbers, NOT  text, which Excel returns an answer how many cells have no data in them.

CountIf:

Counts the number of cells with grade4s,2, in cells A2 through A5 returning value to2 decimal places.

=COUNTIF(A2:A5,"grade4s")

SumIf:

I use this for adding up all the credits or all the debits in a column of number, e.g. the bank statement.

SUMIF(A1:A400,">0") adds all the positive values; and change the sign to "<0" adds all the negative value.

The value can be0 or any other number, e.g. total sales in product range >10,000 unit currency.

Product:

The calculation sum total or function total is the product of a formula. 

Sum

Casts and totals numbers in a range horizontally, or vertically.

COUNTBLANK counts the number of empty cells in the selected range of cells. eg: =COUNTBLANK(A4:A12)

COUNTIF Counts the number of cells that meets the certain condition you specify. eg: COUNTIF($P$6:$Q$15,P21) - This counts the number of cells in P6 to Q15 with a criteria P21

PRODUCT Used to multiply all the cells you include in the formula

SUM adds the total of numbers you select in specific cells.

SUMIF is used to calculate the total of cells specified by given condition and criteria.The formula has Range(Total cells you want to evaluate), Criteria (condition or criteria), Sum_range(Select these colomns where you need the number to be added to the criteria)

SUMIF(Range; Criteria; SumRange)

To sum up only negative numbers: =SUMIF(A1:A10;"<0")

=SUMIF(A1:A10;">0";B1:10) - sums values from the range B1:B10 only if the corresponding values in the range A1:A10 are >0.