Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
A fair coin is tossed times. Every string of heads and tails is equally likely. Find the probability of exactly heads. Find the probability of at least heads. Then find the probability that the number of heads is larger than the number of tails. Give each as a decimal to four places.
With two dice, a total of has ways out of . With three dice the ways for the totals to are out of . Exactly successes in trials is counted by choosing their places: . For at least one, use the complement.
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. Exactly 7 heads. strings, so .
Step 2. At least 12 heads. . So .
Step 3. More heads than tails. By symmetry, more heads and more tails are equally likely. The two events together have probability , so more heads has probability .
Answer: , and .
Log in to join the discussion.
Loading…