The average mass of Ken, David and Kelvin is 42 kg. David is 6 kg heavier than the average mass of Ken and Kelvin. Ken is 6kg heavier than Kelvin. Find David's mass.

Answer 1

Kelvin --- x
Ken ----- x+6
average of Kelvin and Ken = (2x+6)/2 = x+3
David = (x+3) + 6 = x+9

(x + x+6 + x+9)/3 = 42
3x + 15 = 126
3x = 111
x = 111/3 = 37

David is 37+9 = =46

check:
Kelvin --> 37
Ken----> 43
David ---> 46

average of Kelvin and Ken = (37+43)/2 = 40
Is David 6 more than that ? YES
All is good