7/8 divided by 420 = 7/8 x 1/420 by inverting
& multiplying
= 7/3360 by multiplying tops together & bottoms together
= 1/480 inch reducing fraction by dividing top & bottom
by 7
(and yes, I know that top is called numerator & bottom is
called denominator, otherwise known as upstairs & downstairs)
Could also work by cross-cancelling earlier, dividing 7 by 7
= 1 and dividing 420 by 7 = 60
leaving 1 x1 on the top & 8 x 60 on the bottom. Will get
same result as before, 1/480 inch.
