UGC NET Paper 1 GA 2007 June Solved Paper

Question : 34 of 50

Marks: +1, -0

Out of four numbers, the average of the first three numbers is thrice the fourth number. If the average of the four numbers is 5, the fourth number is:

Validate

Solution:

Let the four nos. be

x_1, x_2, x_3,

and

x_4

ATQ

{x_1+ x_2+x_3} /3=3x_4

⇒{x_1+ x_2+x_3} =9x_4

...(1)
also

{x_1+ x_2+x_3+x_4} /4=5

{x_1+ x_2+x_3+x_4} =20

...(2)
From eqn (1) and (2)

10x_4 = 20 ⇒ x_4 = 2

∴ the fourth number = 2.

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