Our photograph shows the ornate Eastgate Clock in Chester, England. Clocks are a rich source of mathematical inspiration ... remember Photographs #35, #48, #55? However, we are thinking here about clock angle problems. For example, at what times do the two hands of the clock exactly coincide (meet at zero angle)? An obvious starter is 12 noon, but then it gets more difficult. Five minutes past one is not right, because the hour hand has then moved just past the ‘one’. You might think about similar problems with the angle between the hands at 180° or 90°. A reverse problem is to ask say, what is the exact angle between the hands at 2:30?
