How can I count the no. of rows in a sheet depending on the values in 2
columns ?

Eg:
Suppose I have two columns in an excel sheet viz

ColA ColB
1 1
2 1
1 2
2 1
1 2
2 0
2 1


I want to count the nos. of 1's in colB iif value in colA for the same row
is "2" ?
I dont want to use a filter.

Result for above example should be:
The count result for the above example should be 3 due to following 3 rows
ColA ColB
2 1
2 1
2 1