Hello!
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As to: 49mm equals how many inches.
We know 1 in = 2.54cm and we know 10 mm = 1cm. so we now multiply:
49mm*(1cm/10mm)*(1in/2.54cm) = 1.93 inches
Notice how I turned the equalities into unit factors: in other words that 1in = 2.54 cm implies our conversion factors (1in/2.54 cm) and (2.54cm/1in) depending on whether we want to convert cm to in or vice versa.
I hope that this helps!

