My mother has 4 children. The youngest is 3 and the oldest is 7. What is a reasonable total of all 4 childrens ages added together?
a. 14
B. 10
C. 20
D. 25
the average age of the two extremes is 5. So, with 4 children, 20 is a reasonable guess.
I think if you listed all possible ages (including twins and triplets) you will come up with a figure close to 20.