Bunuel wrote:

On a recent trip, Mary drove 50 miles. What was the average speed at which she drove the 50 miles?

(1) She drove 30 miles at an average speed of 60 miles per hour and then drove the remaining 20 miles at an average speed of 50 miles per hour.

(2) She drove a total of 54 minutes.

Target question: What was Mary's average speed for the 50-mile trip?Average speed = (total distance)/(total travel time)

= (50 miles)/(total travel time)

As you can see,

we need only determine the total travel time in order to answer the

target question.

Statement 1: She drove 30 miles at an average speed of 60 miles per hour and then drove the remaining 20 miles at an average speed of 50 miles per hour. For both parts of her journey, we COULD determine the travel time, so we COULD find the

total travel time, which means we COULD calculate

Mary's average speedSince we COULD answer the

target question with certainty, statement 1 is SUFFICIENT

Statement 2: She drove a total of 54 minutes. Perfect! Her

total travel time is 54 minutes, so we COULD calculate

Mary's average speedSince we COULD answer the

target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,

Brent

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