Question

The mean of 2, 7, 6 and x is 15 and mean of 18, 1, 6, x and y is 10. What is the value of y? 

(a) 5 

(b) 10 

(c) - 20 

(d) 30

Answer 1

Correct answer is (c) - 20

Mean = \(\cfrac{sum\,of\,observations}{number\,of\,observations}\)

⇒ 15 = \(\cfrac{2+7+6+x}4\)

⇒ 60 = 15 + x 

⇒ x = 45 …….(1) 

Now,

Mean = \(\cfrac{sum\,of\,observations}{number\,of\,observations}\)

⇒ 10 = \(\cfrac{18+1+6+x+y}5\)

⇒ 50 = 25 + x + y 

⇒ y = 25 – x

⇒ y = 25 – 45 [From (1)] 

⇒ y = - 20