Groups each containing 3 boys are to be formed out of 5 boys. A, B, C, D and E such that no group can contain both C and D together. What is the maximum number of such different groups?
Correct answer: C. 7
- A. 5
- B. 6
- C. 7
- D. 8
Explanation
There are 5C3 = 10 groups of 3 boys. Groups containing both C and D are formed by choosing the third boy from A, B or E, so there are 3 invalid groups; therefore, 10 - 3 = 7 valid groups. The likely distractor is 8, which undercounts the groups containing both C and D by one.
Last updated
About Sequences and Series
Sequences describe ordered terms formed by a pattern, while series represent the sum of those terms. Questions cover arithmetic and geometric sequences, their nth terms, common difference or ratio, finite sums, and applications, with the sequence itself kept distinct from the corresponding series.
Practise Algebra
269 free Algebra MCQs from Mathematics, each with the correct answer and an explanation. Unlimited attempts, no account needed.
Exams that ask Mathematics questions like this
Mathematics is on 67 papers prepared for on TestUstad, and all of them draw the same bank, so this question is worth knowing for every one of them.