How many different selections of 4 letters can be made of word TELEPHONE if
a)there are no Es?
b)there is exactly 1 E?
c)there are no restrictions?
a) There are 7 letters, t, e, l, p, h, o, and n. We dn't want e so we have 6 letters. There are 15 ways to leave two letters out, so our answer is 15.
b) we now want 3 letters from the 6 letters. There are 20 ways to get it.
c) we want 4 letters from 7 letters. there ar 35 possibilities.