When this formula is copied down the column, it correctly reports a running total on each row.
This formula uses what is called a "mixed reference" to create an "expanding range". A mixed reference is a reference that includes both absolute and relative parts.
In this case, the SUM formula refers to the range C6:C6. However, the first reference to C6 (on the left of the colon) is absolute and is entered $C$6. This "locks" the reference so that it won't change when copied.
On the right of the colon, the reference is relative, and appears as C6. This reference will change as the the formula is copied down the column.
The result is a range that expands by one row each time it is copied down:
=SUM($C$6:C6)// formula in D6=SUM($C$6:C7)// formula in D7=SUM($C$6:C8)// formula in D8
Working from the inside out, the COUNTIF function is set up to count the value "blue" that appears in column B: COUNTIF ( $B$5:B5 , "blue" ) Note the left side of the range reference is locked ($B$5) and the right side is relative (B5)...
The Excel SUM function returns the sum of values supplied. These values can be numbers, cell references, ranges, arrays, and constants, in any combination. SUM can handle up to 255 individual arguments.
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