Question

Time Elapsed (hr) Distance Run (mi)
2 13.5
4 27.5
7 48.5
Larry recorded his time as he ran.

What was his average speed from hour 2 to hour 4?

What was his average speed from hour 4 to hour 7?

Did he speed up, slow down, or stay the same?

Answer 1

To find Larry's average speed during the specified time intervals, we will use the formula for average speed, which is:

\[
\text{Average Speed} = \frac{\text{Total Distance}}{\text{Total Time}}
\]

### Average Speed from Hour 2 to Hour 4

1. **Calculating the Total Distance from Hour 2 to Hour 4:**
- Distance at Hour 4 = 27.5 miles
- Distance at Hour 2 = 13.5 miles
- Distance covered from Hour 2 to Hour 4:
\[
\text{Distance} = 27.5 - 13.5 = 14 \text{ miles}
\]

2. **Calculating the Total Time from Hour 2 to Hour 4:**
- Time from Hour 2 to Hour 4 = 4 - 2 = 2 hours

3. **Calculating Average Speed:**
\[
\text{Average Speed} = \frac{14 \text{ miles}}{2 \text{ hours}} = 7 \text{ miles per hour}
\]

### Average Speed from Hour 4 to Hour 7

1. **Calculating the Total Distance from Hour 4 to Hour 7:**
- Distance at Hour 7 = 48.5 miles
- Distance at Hour 4 = 27.5 miles
- Distance covered from Hour 4 to Hour 7:
\[
\text{Distance} = 48.5 - 27.5 = 21 \text{ miles}
\]

2. **Calculating the Total Time from Hour 4 to Hour 7:**
- Time from Hour 4 to Hour 7 = 7 - 4 = 3 hours

3. **Calculating Average Speed:**
\[
\text{Average Speed} = \frac{21 \text{ miles}}{3 \text{ hours}} = 7 \text{ miles per hour}
\]

### Conclusion

- **Average Speed from Hour 2 to Hour 4:** 7 miles per hour
- **Average Speed from Hour 4 to Hour 7:** 7 miles per hour

Since Larry's average speed remains the same (7 miles per hour) between both intervals, he **stayed the same** in terms of speed.