A telecommunication company has 7 satellites, two of which are sending a week signal. If two are picked at random without replacement, find the probability that both are sending a week signal
2/7 is the probability that the first satellite sends a weak signal. That leaves 6, one of which sends a weak signal. So the probability that the second also sends a weak signal is 1/6. Combine these and we get 2/7×1/6=1/21.
