in english 12in=1foot 3ft=1yd 16oz=1lb 8oz=1cup 3tsbs=1tbs 2c=1pt 2pt=1qt 4qt=1gal 32 F⁰=freezing 2hundred something=boiling
metric is nice because everything is in multiplules of 10
and also this exerpt from a book "<span>In metric, one milliliter of water occupies one cubic centimeter,
weighs one gram, and requires one calorie of energy to heat up by one
degree centigrade which is 1 per cent of the difference between its
freezing point and its boiling point. An amount of hydrogen weighing the
same amount has exactly one mole of atoms in it. Whereas in the American
system the answer to <em>'How much energy does it take to boil a
room-temperature gallon of water?'</em> is go **** yourself because you
can't directly relate any of those quantities "</span>
A simple trick is to look at the numerator and denominator separately, if they're both perfect squares then you're good (4, 2^2, check. 9, 3^2, check.)
3/7 multiplied by 21 = 3/7 x 21 = 9 = 3/7 x 21/1 = 63/7 = 9
Or if you can't do the math - Think of a pizza with 21 slices . Now cut this pizza into 7 equal parts. You will find that each part contains exactly 3 slices. Now, eat 3 of these parts. With three slices in each part, you ate 9 slices - which is three sevenths of 21.
