Answer:
The equation to describe the relationship between Elena distance:
a) D = 4.34 miles, b) D = 4.25 miles and c) 12D = M + 3N miles.
Solution:
Given, Elena bikes 20 minutes each day for exercise. Â
We have to write an equation to describe the relationship between her distance in miles, D, and her biking speed, in miles per hour, Â
We know that, distance travelled = speed  time
a. At a constant speed of 13 miles per hour for the entire 20 minutes Â
Her speed is 13 miles per hour. Â
Then, distance D miles = 13 miles per hour  20 minutes
b. At a constant speed of 15 minutes per hour for the first 5 minutes, then at 12 miles per hour for the last 15 minutes Â
Now, total distance travelled = distance travelled with 15 mph + distance travelled with 12 mph
c. At a constant speed of M miles per hour for the first 5 minutes, then at N miles per hour for the last 15 minutes
Now, total distance travelled = distance travelled with M mph + distance travelled with N mph
Hence, a) D = 4.34 miles, b) D = 4.25 miles and c) 12D = M + 3N miles.