Multiple choice

A motorbike rider traveled for two hours. Was the rider's average speed during the second hour less than 28 kilometers per hour? (1) The rider covered a total of 90 kilometers over the two hours. (2) The distance covered in the first hour was 20 kilometers less than the distance covered in the second hour.

  1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

  2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

  3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

  4. EACH statement ALONE is sufficient.

  5. Statements (1) and (2) TOGETHER are NOT sufficient.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let d1 and d2 be distances in hour 1 and 2. (1) d1 + d2 = 90. (2) d2 - d1 = 20. Together: 2*d2 = 110, d2 = 55. Average speed in 2nd hour = 55 km/h. This is not less than 28. Both statements are needed to find d2.

AI explanation

Statement one provides the total distance of 90 kilometers, but without knowing the split between the two hours, the second hour's speed could be more or less than 28 km/hr. Statement two provides a relationship between the distances, but without the total distance, we still cannot find the exact distance for the second hour. Using both statements together, we form the equation d + (d + 20) = 90, which solves to show the second hour's distance was 55 kilometers, confirming the speed was 55 km/hr and definitively answering the question.

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