Problem
COM-B1-M01-P014 Exactly Three Ones
#14
★★★☆☆ Level 3 of 5
How many binary strings of length \(10\) contain exactly three ones?
It is enough to choose the positions of the three ones.
Choose \(3\) positions out of \(10\) for the ones; all remaining positions are zeros. This gives \(120\) strings.
The combinations formula can be introduced as a result of choosing positions.