Question

the mean of 2,7,6 and x is 15 and the 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

In ( 1 ) case:- The average of 2, 7, 6 and x is 5

⇒$\frac{2+7+6+x}{4}=5$

⇒$\frac{15+x}{4}=5$

⇒$15+x=20$

⇒$x=20-15$

⇒$x=5$------( 1 )

In ( 2 ) case:- the average of 18, 1, 6, x and y is 10

⇒$\frac{18+1+6+x+y}{5}=10$

⇒$\frac{25+x+y}{5}=10$

⇒$\frac{25+5+y}{5}=10$ -----from( 1 )

⇒$\frac{30+y}{5}=10$

⇒$30+y=50$

⇒$y=50-30$

⇒$y=20$