Question

Use the image to answer the question.

A coordinate plane for distance versus time.
▶Click for Long Desc

Riley is training to run a 5-mile race. The graph represents the distance (miles) she ran with respect to time (minutes) in her first training run. Over which time interval did she run the fastest, [0,8]
or [2,11]
? Justify your answer in 1–2 sentences.

(2 points)

Answer 1

From the graph: d(0)=0, d(8)=4, d(2)=1, d(11)=5. Average speed on [0,8] = (4−0)/8 = 0.5 mi/min, on [2,11] = (5−1)/9 = 4/9 ≈ 0.444 mi/min, so she ran fastest on [0,8].