answer : d) 48
Given, the sum of 7 numbers=12*7=84
Sum of the 4 smallest numbers=4*8=32----(a)
Sum of the 4 greatest numbers=4*20=80 (here 3 numbers are different from the smallest numbers, one number is common to both smallest and greatest numbers)--(b)
To find:- sum of 3 greatest numbers-sum of 3 smallest numbers
3S+common number+3G+common number=80+32=112
=84+common number=112-84=28
So, common number=28
Now, from(a), 3S+common number=32
Or, 3S=32-28=4
from(b), 3G+common number=80
Or, 3G=80-28=52
So, 3G-3S=52-4=48
Where 3S and 3G denote the sum of 3 greatest numbers and sum of 3 smallest numbers respectively.
Ans. (D)