An L-shaped sheet of card is 14 centimetres across and 9 centimetres tall, with a piece 5 centimetres across and 4 centimetres tall missing from its top right corner, so it has six straight edges. A ribbon is glued all the way round those six edges. How long is the ribbon?

Explicación

Following the outline covers 14 along the bottom, 5 up the right, 5 leftwards under the notch, 4 up its side, then 9 back along the top and 9 down the left, which totals exactly what the uncut rectangle would have needed. Quoting 106 answers how much card there is rather than how far the ribbon travels, and those two questions are counted in different kinds of unit.