The average of X and Y is 40, that of Y and Z is 38, and that of Z and X is 42. Find the average of X, Y and Z.

Correct option is B

Given:

Average of X and Y = 40

Average of Y and Z = 38

Average of Z and X = 42

Formula Used:

Average of two numbers $$=\dfrac{\text{Sum of the two numbers}}{2}$$​​

Solution:

From the given information:

​$$\dfrac{X + Y}{2} = 40$$​

X + Y = 80

$$\dfrac{Y + Z}{2} =$$​ 38

Y + Z = 76

​$$\dfrac{Z + X}{2} = 42$$​

Z + X = 84

Now, we add all three equations:

(X + Y) + (Y + Z) + (Z + X) = 80 + 76 + 84

2X + 2Y + 2Z = 240

X + Y + Z =$$\dfrac{240}{2}$$​= 120

Average of X, Y, and Z $$= \dfrac{X + Y + Z}{3} = \dfrac{120}{3} = 40$$​