The mean of the heights of three buildings A, B and C is 14.2m. The mean of the heights of five buildings A, B,C, D and E is 14.8m. Find the mean of the heights of the buildings D and E.

Work Shown:

s = sum of the heights of buildings A,B,C

s/3 = mean of the heights of buildings A,B,C

s/3 = 14.2

s = 3*14.2

s = 42.6

The buildings A,B,C have their heights add up to 42.6

r = sum of the heights of buildings A,B,C,D,E

r/5 = mean of the heights of buildings A,B,C,D,E

r/5 = 14.8

r = 5*14.8

r = 74

r-s = (sum of heights of A,B,C,D,E)-(sum of heights of A,B,C)

r-s = sum of the heights of buildings D and E

r-s = 74-42.6

r-s = 31.4

(r-s)/2 = mean height of buildings D and E

(r-s)/2 = 31.4/2

(r-s)/2 = 15.7 meters is the average height of buildings D and E.