Bunuel wrote:

A recent census of all American females revealed that the current average age that females in America marry is 27. The average age that females have their first child is also 27. According to a census taken 20 years ago, the average ages that females married and had their first child were 23 and 25 years, respectively.

If the information recorded in the two censuses is true, which of the following must also be true about American females?

(A) Currently, more females are having their first child before they marry than they did 20 years ago.

(B) On average, females are currently waiting longer to have their first child than they did 20 years ago.

(C) Females today are more likely to complete their education before getting married and having children than they were 20 years ago.

(D) On average, females had larger families 20 years ago than they have today.

(E) Twenty years ago, most females waited at least two years after they were married to have their first child.

OFFICIAL EXPLANATION:

B. This question asks you to come up with a conclusion based on the information in the paragraph.

Notice that the question asks you for what must be true rather than what could be true. So you can cross out any answers that aren’t absolutely true given the data in the paragraph.

All you know from the paragraph is the average marrying age for females today and 20 years ago and the average age that females have their first child today compared to 20 years ago. The paragraph says nothing about the number of children females have or had, so you can easily wipe Choice (D) out of contention. Furthermore, the paragraph provides no explanation for why the data has changed over the years, so you can’t know the reason that the average age has increased. So Choice (C) can’t be right.

Don’t choose an answer based on an assumption or your own experience. The paragraph merely reports data instead of commenting on it, and it treats the age of marrying and having one’s first child as two separate statistics. You can’t make assumptions about how the two sets of data are related.

That means that Choice (A) doesn’t have to be true. Just because the average age for marrying and having a first child are currently the same doesn’t mean that more American females are having their first child before they marry. For example, the increased marrying age could be the result of females who marry when they’re older and have no children. Eliminate Choice (E) for the same reason. You can’t assume from these limited statistics that the females who are 23 when they marry are the ones who are having their first child at 25. There are too many other variables in the population.

The only thing you know for sure is that, because the average age for having a first child has risen over the last 20 years, on average, females are having their first child at a later age than they did 20 years ago. Choice (B) is the only answer that must be true.

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