The Clock in the Mirror★☆☆about 3 min
The Dog That Did Not Bark★☆☆about 4 min
Measuring a Building by Its Shadow★★☆about 4 min
The Round-Trip Average Speed★★☆about 5 min
Twenty Percent Off, Then Ten Percent Up★☆☆about 3 min
Three-Cent and Five-Cent Stamps★★☆about 5 min
Poison Hidden in the Ice★★☆about 5 min
The Missing Newspapers★☆☆about 3 min
The Four-Lamp Code★☆☆about 4 min
The Shifted Note★☆☆about 4 min
A Sixty-Four Player Tournament★☆☆about 3 min
Three Sticks, One Triangle★★☆about 4 min
The Diagonal of a 3 by 4 Room★☆☆about 4 min