Pythagorean Theorem is:
c² = a² + b²
Let’s find the values of a and b.
Looking at the image provided in the question we have 2 number already, 70 and 120.
Let’s name the side with length 120 as a, and the side with length 70 as b.
Then we should substitute these values into the Pythagorean Theorem:
c² = 120² + 70²
c² = 14400 + 4900
c² = 19300
Then we should work out the value of c by square rooting both sides:
√c = √19300
c = 138.92444
Therefore the ball would have to be hit a total of 138.92444 units.
If you have to round, that would be 139 units.