Question 15 Marks
In a true-false test containing 50 questions, a student is to be awarded 2 marks for every correct answer and (-2) for every incorrect answer. (and 0 for not attempting any answer). If Yash secured 94 marks in a test, What are the possibilities of his marking correct or incorrect answer?
Answer
View full question & answer→Marks scored $=94$
So, minimum correct answers $=\frac{94}{2}=47$
Case I Correct answer $=47$
Marks for correct answers $=2$
Marks for 47 correct answers $=47 \times 2=94$
Marks for incorrect answers $=0$
So, no incorrect answers and 3 unattempted answers.
Case II Correct answers $=48$
Marks for 48 correct answers $=48 \times 2=96$
Marks scored $=94$
Marks obtained for incorrect answer $=94-96=-2$
Marks for one incorrect answer $=-2$
Number of incorrect answers $=(-2) \div(-2)=1$
$\therefore 48$ correct answer, 1 incorrect answer and 1 unattempted answer.
Case III Correct answer $=49$
Marks for 49 correct answers $=49 \times 2=98$
Marks scored $=94$
Marks for incorrect answers $=94-98=-4$
Number of incorrect answers $=(-4) \div (-2)=2$
Thus, number of questions $=49+2=51$
Whereas, total number of questions is 50 .
So, this case is not possible.
Thus, the possible ways are
47 correct answers, 3 unattempted answers
or 48 correct answers, 1 unattempted answer and 1 incorrect answer.
So, minimum correct answers $=\frac{94}{2}=47$
Case I Correct answer $=47$
Marks for correct answers $=2$
Marks for 47 correct answers $=47 \times 2=94$
Marks for incorrect answers $=0$
So, no incorrect answers and 3 unattempted answers.
Case II Correct answers $=48$
Marks for 48 correct answers $=48 \times 2=96$
Marks scored $=94$
Marks obtained for incorrect answer $=94-96=-2$
Marks for one incorrect answer $=-2$
Number of incorrect answers $=(-2) \div(-2)=1$
$\therefore 48$ correct answer, 1 incorrect answer and 1 unattempted answer.
Case III Correct answer $=49$
Marks for 49 correct answers $=49 \times 2=98$
Marks scored $=94$
Marks for incorrect answers $=94-98=-4$
Number of incorrect answers $=(-4) \div (-2)=2$
Thus, number of questions $=49+2=51$
Whereas, total number of questions is 50 .
So, this case is not possible.
Thus, the possible ways are
47 correct answers, 3 unattempted answers
or 48 correct answers, 1 unattempted answer and 1 incorrect answer.