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What is the average height of the class? I. Average height of the class decreases by 1 cm i we exclude the tallest person of class whose height is 56 cm. II. Average height of the class increase by 1 cm if we exclude the shortest person o the class whose height is 42 cm.

if the data in Statement I alone is sufficient to answer the question but the data in Statement II alone is not sufficient to answer the question.
if the data in Statements II alone is sufficient to answer the question but the data in Statement I alone is not sufficient to answer the question.
if the data in Statement I and II together are necessary to answer the question.
if the data in Statement I and II together are not sufficient to answer the question.

Correct Answer: if the data in Statement I and II together are necessary to answer the question.

Explanation:

Let x be the average height of the class and n be the number of students in the class.
Consider statements I alone
xn - 56 = (x + 1)(x -1)
⇒ x + n = 57 .............(i)
Hence, the value of x cannot be found. So, I alone is not sufficient.
Consider statement I alone:
xn - 42 = (x + 1)(n - 1)
⇒ x - n = 41 .............(ii)
Hence, the value of x cannot be found. So, II alone is not sufficient.
Both the statements together are suficient as the value of x can be found by solving (i) and (ii)

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What is the average height of the class? I. Average height of the class decreases by 1 cm i we exclude the tallest person of class whose height is 56 cm. II. Average height of the class increase by 1 cm if we exclude the shortest person o the class whose height is 42 cm.

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