Discussion

Explanation:

Let
x = Number of correct answers
y = Number of wrong answers
z = Number of unattempted questions.

Given, x + y + z = 100    …(1)
6x – 2y – z = 321    …(2)
(1) + (2) : 
⇒ 7x - y = 421
⇒ y = 7x - 421

We know y ≥ 0
Hence, 7x - 421 ≥ 0
⇒ x ≥ 421/7
⇒ x ≥ 60.14

∴ Least value of x can be 61, for which y = 6 and z = 33.
Next possible value of x = 62, for which y = 13 and z = 25.
Next possible value of x = 63, for which y = 20 and z = 17.
Next possible value of x = 64, for which y = 27 and z = 9.
Next possible value of x = 65, for which y = 34 and z = 1.

∴ There are 5 ways of attempting the exam.

Hence, option (b).

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