(5 min)Review canceling
When you are drawing cards out of a deck, you may have noticed that
sometimes the denominator can get very big. You may find that it is
52 x 51 x 50 x 49 x 48 which is 311,875,200. Well this number might
be too big to fit into your calculator, so you might get an error.
Anyway, it is a nuisance to have such a big number and then try to
reduce it. An easier way to do it is to cancel like factors
in the numerator and denominator before you multiply, like
This is the probability of drawing 3 spades in a
Remember that the factors you cancel don't need to be above each other in
the same fraction. In the above fraction, you see that the 4 in the
denominator of the first fraction can be canceled with the 4 in the
numerator of the second fraction. Try this:
3 5 11 18
--- x --- x ---- x ---- = ?
11 18 5 2