POSSIBILITIES AND PROBABILITY
POWERS AND ROOTS
42 . Counting the Possibilities
The fundamental counting principle: If there are m ways one event can
happen and n ways a second event can happen, then there are m × n ways
for the two events to happen. For example, with 5 shirts and 7 pairs of pants
to choose from, you can have 5 × 7 = 35 different outfits.
43 . Probability
For example, if you have 12 shirts in a drawer and 9 of them are white, the
probability of picking a white shirt at random is This probability
can also be expressed as 0.75 or 75%.
44 . Multiplying and Dividing Powers
To multiply powers with the same base, add the exponents and keep the
same base:
x^3 × x^4 = x3+4 = x^7
To divide powers with the same base, subtract the exponents and keep
the same base:
y^13 ÷ y^8 = y13−8 = y^5
