arithmetic mean

Question

The average age of 10 friends is 32 years. If 3 of them average 28 years, and 5 others average 34 years, what is the average age of the remaining 2 people?

Answer 1

You could write this as an algebraic equation.  [2x+3(28)+5(34)]/10 = 32

 

Two people of unknown age x, plus 3 at age 28 and 5 at age 34 all average an age of 32...

 

An average is the total ages divided by the number of people (10).

 

So now solve for x.  (2x+254)/10 = 32

2x+254 = 320

2x = 66

x = 33

 

The average age of the remaining two people is 33.

Answer 2

10*32=320

320-3(28)-5(34)=320-84-170

320-254=66 and 66/2=33 years