Open Middle®
Directions: Using the digits 1 to 9 at most two times each, place a digit in each box to make a circle with the least possible area.
Hint
How do we ensure that the digits we choose create a circle? How do the digits we choose affect the size of our circle?
Answer
The least possible area we can have comes from the equation 9x2 + 9y2 = 1 for an area of ~0.35 units2.
Source: Robert Kaplinsky
