Question:medium

A test has 50 questions. A student scores 1 mark for a correct answer, –1/3 for a wrong answer, and –1/6 for not attempting a question. If the net score of a student is 32, the number of questions answered wrongly by that student cannot be less than:

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When minimizing or maximizing one variable, use the constraints to find the range of possible values.
Updated On: Jun 25, 2026
  • 12
  • 3
  • 4
  • 9
  • 2
Show Solution

The Correct Option is B

Solution and Explanation

To solve this problem, we need to determine the number of questions that the student answered wrongly, given certain conditions.

Let's denote the following variables:

  • Let \(x\) be the number of correct answers.
  • Let \(y\) be the number of wrong answers.
  • Let \(z\) be the number of questions not attempted.

The total number of questions is 50, so we have:

\(x + y + z = 50\)

For each correct answer, the student scores 1 mark. For each wrong answer, the student loses \(\frac{1}{3}\) of a mark. For each question not attempted, the student loses \(\frac{1}{6}\) of a mark.

The net score of the student is given as 32. Thus, we can formulate the score equation as:

\(x - \frac{1}{3}y - \frac{1}{6}z = 32\)

We now have two equations:

  • \(x + y + z = 50\) (Equation 1)
  • \(x - \frac{1}{3}y - \frac{1}{6}z = 32\) (Equation 2)

To simplify and solve these equations, let's multiply Equation 2 by 6 to eliminate the fractions:

\(6x - 2y - z = 192\) (Equation 3)

Now, we'll subtract Equation 1 from Equation 3:

\((6x - 2y - z) - (x + y + z) = 192 - 50\)

This simplifies to:

\(5x - 3y - 2z = 142\) (Equation 4)

From Equation 1, we can express \(z\) as:

\(z = 50 - x - y\) (Equation 5)

Substitute Equation 5 into Equation 4:

\(5x - 3y - 2(50 - x - y) = 142\)

Simplify to get:

\(5x - 3y - 100 + 2x + 2y = 142\)

Which further simplifies to:

\(7x - y = 242\) (Equation 6)

From Equation 6, we can express \(y\) in terms of \(x\):

\(y = 7x - 242\)

Now, ensure \(y\) is a non-negative value:

Solving \(7x - 242 \geq 0\), we get \(x \geq \frac{242}{7} = 34.57\).

Thus, \(x\) must be at least 35 because \(x\) is an integer.

Substitute \(x = 35\) back in:

  • \(y = 7(35) - 242 = 3\)
  • \(z = 50 - 35 - 3 = 12\)

The minimum number of questions answered wrongly is 3.

Therefore, the correct answer is 3.

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