There are 4 blood types, and not all are equally likely to be in blood banks. 49% of donations are type O blood, 27% of donations are type A blood, 20% of donations are type B blood, and 4% of donations are type AB blood. A person with type A blood can safely receive blood transfusions of type O and type A blood. If three donations are made, what is the probability that at least 1 of them can be safely used in a blood transfusion on someone with type A blood?

Type O and type A donations are safe for someone with type A blood, so the probability a donation is safe is 0.49 + 0.27 = 0.76. It is easier to find the probability that none of the three donations is safe: each must be type B or AB, with probability 0.20 + 0.04 = 0.24, giving 0.24³ = 0.013824. Thus, the probability of at least one safe donation is 1 − 0.013824 = 0.986176, or about 0.9862. The correct choice is D, 0.9862.

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