Given a group of
n object. We want to make a selection of
k objects out of the n object. This can be done in
C(n, k) many ways, where

,
where k!=1*2*3*...(k-1)*k
Thus, we can do the selection of 3 cd's out of 5, in C(5,3) many ways,
where

Answer: 10
Answer:
37 ft
Step-by-step explanation:
The ladder forms a right triangle as it elan's against the wall of the boat house.
Thus, the length of the ladder can be determined using Pythagorean theorem.
c² = a² + b²
c = length of ladder
a = 35 ft
b = 12 ft
Plug in the values
c² = 35² + 12²
c² = 1,225 + 144
c² = 1,369
c = √1,369
c = 37
Therefore, to reach the roof of the boathouse, the length of the ladder = 37 ft