math
posted by tish .
A British company is sending you measurements for a table to build in your factory. The table top must be 50 cm × 75 cm. Your machine calibrates in inches. Find the size of the table in inches. (1 cm = .39 in)

While 1cm = 0.39 inch is a good approximation to within 1%, I usually use one inch = 2.54 cm, which is exact!
Using the given conversion factor,
50 cm = 50cm *0.39"/cm = 19.5"
75 cm = 75cm *0.39"/cm = 29.25"
Using the exact value of 1"=2.54cm,
50 cm = 50 / 2.54 = 19.69"
75 cm = 75 / 2.54 = 29.53"
So there is a measurable difference. 
50 cm X 75 cm