If using the method of completing the square to solve the quadratic equation $x^{2}-15 x+22=0$, which number would have to be added to "complete the square"?

Step 1 ：Given the quadratic equation \(x^{2}-15 x+22=0\).

Step 2 ：To complete the square, we need to make the quadratic equation in the form of \((x-a)^2 = b\).

Step 3 ：The coefficient of \(x\) in the equation is \(-15\), so we need to divide it by \(2\) and square the result to get the number that needs to be added to complete the square.

Step 4 ：Calculate \((-15/2)^2\) to get \(56.25\).

Step 5 ：Final Answer: The number that needs to be added to complete the square is \(\boxed{56.25}\).