Question

An unlimited number of coupons bearing the letters A, B and C are available. What is the possible number of ways of choosing 3 of these coupons so that they cannot be used to spell BAC?

• A. 15
• B. 18
• C. 21
• D. 27

Answer 1

The correct option is C

21

Each of the 3 places can take 3 letters $\Rightarrow$ 27. But we don't want the combination (A, B, C) $\Rightarrow$ 3! = 6 are out $\Rightarrow$ 27-6 = 21. Hence, choice (c) is the right answer.