A tray contains 11 chocolate chip cookies and 15 oatmeal raisin cookies. How many ways can a child select 4 cookies that include at least 1 chocolate chip cookie?

Answer 1

number without any restriction
= C(26,4) = 14950

number which are all oatmeal
= C(15,4) = 1365

so, the number with at least one chocolate chip
= 14950-1365 = 13585