Open Middle®
Directions: Using the digits 1 to 9 at most one time each, fill in the boxes to make the smallest (or largest) sum.
Hint
How can we make a really big fraction? How can we make a really small difference from fractions? If improper fractions are allowed, the numerators should be as big as possible and the denominators as small as possible. Otherwise, we want the fractions to each be as close to one as possible.
Answer
9/1 + 8/2 or 8/9 + 6/7
Source: Robert Kaplinsky
Smallest possible sum is 2/9 + 1/8 = 0,3472222…