If the average (arithmetic mean) of \(x, y\) and \(15\) is \(9,\) and the average of \(x, 2y\) and \(2\) is \(7,\) then

[M7MBA]

If the average (arithmetic mean) of \(x, y\) and \(15\) is \(9,\) and the average of \(x, 2y\) and \(2\) is \(7,\) then \(y =\)

A. 5
B. 6
C. 7
D. 8
E. 9

Answer: C

Source: Magoosh

[psarma]

Average of x,y & 15 is 9
i.e (x+y+15)/3 = 9
or x+y=12

Also, average of x,2y & 2 is 7
i.e (x+2y+2)/3 = 7
or x+2y = 19

Subtracting 1st equation from 2nd equation,
we get y = 7

Option C

[Scott@TargetTestPrep]

If the average (arithmetic mean) of \(x, y\) and \(15\) is \(9,\) and the average of \(x, 2y\) and \(2\) is \(7,\) then \(y =\)

A. 5
B. 6
C. 7
D. 8
E. 9

Answer: C

Solution:

We can create the equations:

(x + y + 15)/3 = 9

and

(x + 2y + 2)/3 = 7

Subtracting the first equation from the second, we have:

(y - 13)/3 = -2

y - 13 = -6

y = 7

Answer: C