The inch

The inch is a British unit of length.    

1 inch = 2.54 cm

 Give your answers to the nearest millimetre.
A computer screen measures 17 inches. How many centimetres is this ?  
If a mountain bike measures 26 inches, how long is it in centimetres ?  
How many centimetres does a 3 and a 1/2 inch floppy disc measure ?