In 1980 (before the era of in-vitro fertilization), there were 3,612,258 births in the United States (according to the U.S. Census Bureau), of which 68,339 births were to twins and 1,337 births were to triplets or more.

Question

What was the probability of having multiples (twins or more) in 1980?
Enter as a percent but do not include the % sign. Round to the nearest tenth (e.g., x.x).

What was the probability of a woman giving birth to multiples twice in a row in the pre-IVF era? (Assume that the probabilities for 1980 are representative of the pre-IVF era.)
Enter as a percent but do not include the % sign. Round to 3 decimal places (e.g., .xxx).

If a woman had 10 births in her lifetime in the pre-IVF era, what was the chance that at least one of those births was to multiples? (Assume that the probabilities for 1980 are representative of the pre-IVF era.)
Enter as a percent but do not include the % sign. Round to the nearest tenth (e.g., xx.x).

Answer 1

1.9

Answer 2

12