Binary-answer test sequences: A test has 10 questions, each answered True (T) or False (F). Every candidate answers all questions. How many distinct T/F answer sequences are possible?
Aptitude
Permutation and Combination
Difficulty: Easy
Choose an option
-
A20
-
B40
-
C512
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D1024
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ENone of these
Answer
Correct Answer: 1024
Explanation
Introduction / Context:Each question admits 2 choices (T or F), independently across questions. Counting sequences of independent binary choices leads to a simple power rule, 2^n for n questions.
Given Data / Assumptions:
- n = 10 questions.
- Choices per question = 2 (T or F), independent.
- Every candidate answers all questions.
Concept / Approach:
- Use the multiplication principle: 2 * 2 * … * 2 (10 times) = 2^10.
Step-by-Step Solution:
Number of sequences = 2^10 = 1024Verification / Alternative check:Binary coding analogy: each sequence corresponds to a 10-bit string; total 10-bit strings = 2^10 = 1024.
Why Other Options Are Wrong:
- 512 = 2^9; too small.
- 20 and 40 are unrelated to 2^10.
Common Pitfalls:
- Treating “questions” as dependent when they are independent.
Final Answer:1024