Problem
COM-B1-M03-P005 Positions of Ones
#5
★☆☆☆☆ Level 1 of 5
How many binary strings of length \(6\) contain exactly two ones?
Choose the positions of the two ones.
Choose \(2\) positions out of \(6\). Answer: \(\binom{6}{2}=15\).
Very important model of choosing positions.