posted by Jas .
The average, that is, the arithmetic mean, age of a group of
doctors and lawyers is 40. If the average age of the doctors is 35
and the average age of the lawyers is 50, then what is the ratio of
the number of doctors to the number of lawyers?
let the number of doctors be d
let the number of lawyers be l
total of ages of doctors = 35d
total of ages of lawyers = 50l
total of both groups = 35d+50l
but this is also equal to 40(d+l)
so 40(d+l) = 35d + 50l
40d + 40l = 35d + 50l
5d = 10l
d/l = 10/2 = 2:1