In how many ways is it possible to select one or more letters from those in
INSIPIDITY?
It doesn't matter that there are 4 I's in INSIPIDITY. We can only select
the letters I,N,S,P,D,T,Y. [The fact that there are 4 I's would affect the
probability of selecting I, but does not affect the number of possible
selections.]
We can choose to include I in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include N in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include S in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include P in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include D in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include T in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
We can choose to include Y in our selection or not include it.
That's 2 ways -- include it or not include it in the selection.
So the answer is 2×2×2×2×2×2×2 = 27 = 128 ways.
Edwin
