averages topic

Question

if the average of x and y is 40 and (z-x)² =3600 what could be the average of y and z?

 

(a)10

(b)20

(c)50

(d)65

(e)70

Answer 1

If the average of x and y is 40 then  (x+y)/2 = 40

 

(z-x)² = 3600

we need to solve for x in terms of z

Take square root of both sides

z-x = √3600

z-x = 60

x = z-60

 

Plug z-60 in place of x in (x+y)/2 = 40

(z-60+y)/2 = 40

z-60 + y = 80

z+y = 140

 

We have the total of z+y  so divide that by 2 to get the average

 

(z+y)/2 = 140/2 = 70

 

Your answer is e