Answer:
The average rate is 7/3 miles per hour
Explanation:
* Lets explain how to solve the problem
- The average rate = total distance ÷ total time
- Vanna walked at rate 2 miles per hour for 10 minutes
- She then walked at a rate 3 miles per hour for 5 minutes
- We wants to know her average rate in mile per hour for the 15
minutes period
- We must find the distance she walked in the 10 minutes and
5 minutes
- Remember that the distance = speed × time
∵ 1 hour = 60 minutes
∴ 1 minute = 1/60 hour
∵ She walked at first for 10 minutes
- Change the minutes to hours
∴ She walked for = 10 × 1/60 = 1/6 hour
∵ Her rate (speed) is 2 miles per hour
∴ The distance she walked = 2 × 1/6 = 1/3 miles
∵ She walked at second for 5 minutes
- Change the minutes to hours
∴ She walked for = 5 × 1/60 = 1/12 hour
∵ Her rate (speed) is 3 miles per hour
∴ The distance she walked = 3 × 1/12 = 1/4 miles
∵ The average rate = the total distance ÷ total time
∵ Total distance = 1/3 + 1/4 = 7/12 miles
∵ The total time = 10 + 5 = 15 minutes
- Change the minutes to hours
∵ 15 minutes = 15 × 1/60 = 1/4 hour
∴ The average rate = 7/12 ÷ 1/4 = 7/3 miles/hour
* The average rate is 7/3 miles per hour