### Brain Teasers

# The String Around the Cylinder

A cylinder 48cm high has a circumference of 16cm. A string makes exactly 4 complete turns around the cylinder, while its two ends touch the cylinder's top and bottom (forming a spiral around the cylinder).

How long is the string in cm?

How long is the string in cm?

### Hint

Pythagoras' theorem may help.### Answer

80cm.Finding the length of the string is the same as finding the length of the hypotenuse of a triangle with a height of 48 cm and a base of 64 cm (16 x 4). Using Pythagoras' theorem, you get:

h^2 = 48^2 + 64^2

Solving, h = 80 cm.

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