by Andrew Skidmore
Published February 11 2018 (link)
Liam has a set of ten wooden cubes; each has a different number (from 1 to 10) painted on one face (the other five faces are blank). He has arranged them in a rectangular block with all numbers upright and facing outwards. Each vertical side of the block shows some numbers which can be read as a perfect square. No two squares have the same number of digits.
Which square must be present?