True/False Quiz Scoring Deduction

XAT 2017 · Quantitative Ability & Data Interpretation · Medium · Logical Reasoning

In a True/False quiz, 4 marks are awarded for each correct answer and 1 mark is deducted for each wrong answer. Amit, Benn and Chitra answered the same 10 questions, and their answers are given below in the same sequential order.

AMIT: T T F F T T F T T F BENN: T T T F F T F T T F CHITRA: T T T T F F T F T T

If Amit and Benn both score 35 marks each then Chitra's score will be:

  1. A.

    10

  2. B.

    15

  3. C.

    20

  4. D.

    25

  5. E.

    None of the above

Answer

A

Explanation

Score equation: 4c−(10−c)=35  ⟹  5c=45  ⟹  c=94c - (10 - c) = 35 \implies 5c = 45 \implies c = 9 correct answers. So both Amit and Benn got 9 correct and 1 wrong. Comparing Amit and Benn: Q3: Amit F, Benn T Q5: Amit T, Benn F All other answers are identical. For both to get 9 correct, exactly one of Q3 or Q5 is T and the other is F. Thus the correct key for Q1-Q10 is either: Key A: T T T F T T F T T F (Amit wrong on Q3, Benn wrong on Q5) Key B: T T F F F T F T T F (Amit wrong on Q5, Benn wrong on Q3)

Test Chitra against Key A: Q1: T (corr), Q2: T (corr), Q3: T (corr), Q4: T (inc), Q5: F (inc), Q6: F (inc), Q7: T (inc), Q8: F (inc), Q9: T (corr), Q10: T (inc). Chitra gets 4 correct (Q1, Q2, Q3, Q9) and 6 incorrect. Chitra's score = 4×4−6×1=104 \times 4 - 6 \times 1 = 10.

Test Chitra against Key B: Q1: T (corr), Q2: T (corr), Q3: T (inc), Q4: T (inc), Q5: F (corr), Q6: F (inc), Q7: T (inc), Q8: F (inc), Q9: T (corr), Q10: T (inc). Chitra gets 4 correct (Q1, Q2, Q5, Q9) and 6 incorrect. Score = 4×4−6=104 \times 4 - 6 = 10.

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