Try each question on your own first. Use the Show Answer button only after you have selected your option, then read the explanation and revise the related concept from your chapter notes.
26. How many chords can be drawn through 21 points on a circle?
A. 210
B. 420
C. 105
D. 21
Answer: A. 210
Explanation: A chord needs 2 points. Number of chords = ²¹C₂ = (21 × 20) / 2 = 210.
27. How many 3-digit even numbers can be made using digits 1, 2, 3, 4, 6, 7 if no digit is repeated?
A. 60
B. 120
C. 30
D. 90
Answer: A. 60
Explanation: Unit place can be 2, 4, or 6 (3 ways). Remaining 2 places filled from remaining 5 digits in ⁵P₂ = 20 ways. Total = 3 × 20 = 60.
28. The number of ways in which 5 boys and 3 girls can be seated in a row so that no two girls are together is:
A. 14400
B. 7200
C. 2880
D. 1200
Answer: A. 14400
Explanation: Arrange 5 boys in 5! = 120 ways. 6 gaps created. Choose 3 gaps for girls in ⁶P₃ = 120 ways. Total = 120 × 120 = 14400.
29. The total number of sub-sets of a set containing 5 elements is:
A. 32
B. 25
C. 16
D. 64
Answer: A. 32
Explanation: Total subsets = 2ⁿ = 2⁵ = 32.
30. Find the number of ways of selecting 9 balls from 6 red balls, 5 white balls and 5 blue balls if each selection consists of 3 balls of each colour:
This page contains a chapter-wise objective practice set. Try the questions without checking the answer first, then use the explanation to understand the point you missed. The current page contains 30 questions, so you can practise in smaller sets when you are revising.
Quick revision tip
After the practice set, write down the question numbers you missed and revise only those concepts once more. This makes MCQ practice more useful than repeatedly attempting the same questions without reviewing mistakes.