单选题
Andrew fitted an electric toy car with hard rubber wheels that had deep treads and placed the car on a smooth, flat surface. Andrew started the car and a stopwatch at the same time. Andrew stopped the stopwatch as the car crossed the 75-foot mark. He calculated the results of 3 separate trials as shown in the table below.
Andrew repeated the procedure, except he fitted the car with soft rubber wheels that were smooth and lacked treads. The results are shown in the table below.
| Procedure 1 | |
| Trial Number | Time in seconds |
| 1 | 22.8 |
| 2 | 23.2 |
| 3 | 22.5 |
| Procedure 2 | |
| Trial Number | Time in seconds |
| 1 | 57.0 |
| 2 | 56.2 |
| 3 | 56.9 |
单选题
What was the average time the car with the soft wheels took to cross the 75-foot mark?
【正确答案】
D
【答案解析】The soft wheels data is in the second table. Calculate the average of those three times: (57.0 + 56.4 + 56.7) ÷ 3 = 56.7
单选题
Assuming that the car traveled at a constant speed, approximately how far had the car with hard wheels traveled in Trial 3 after 11.25 seconds?
【正确答案】
B
【答案解析】Since the car traveled at a constant speed, you can set up a proportion between the time and distance of the whole run and the time and distance of the partial run.
单选题
During which procedure and trial did the car travel at the highest speed?
【正确答案】
C
【答案解析】The data in the tables reflects the amount of time the cars took to travel a constant distance. Therefore, the car that finished in the least amount of time traveled at the highest speed.
单选题
Assuming the car in Procedure 1 traveled at a constant speed, approximately how long would it take the car to travel 100 feet?
【正确答案】
C
【答案解析】The first step is to calculate the average speed for all three trials: (22.8+23.2+22.5)÷3=22.8. Next, since the car traveled at a constant speed, you can set up a proportion between the time and distance of the whole run and the time and distance of the partial run: 22.8÷75=0.304 sec/feet. Finally, multiply 0.304 by 100 to get 30.4 seconds.