SAT Subject Test Mathematics Level 2

Third, replace each letter with the simple independent probability it represents by thinking

about one toss of one coin. What’s the probability of getting T? It’s —so replace every T

with . What’s the probability of getting H? It’s also —so replace every H with :

Toss    1 Toss  2 Toss  3 Toss  4 Toss  5

One way:

Another

way:

Another

way:

Another

way:

Another

way:

Another

way:

Finally, because the probability of an event that could occur in more than one way is simply
the sum of the probabilities of the various ways in which the event could occur, multiply
across and add down:

Toss    1 Toss  2 Toss  3 Toss  4 Toss  5

One way:

Another

way:

Another

way:

Another

way:

Another

way: