Respuesta :
Answer:
D.
d = 3t; 90 mi
Step-by-step explanation:
Bicycling A bicyclist traveled at a constant speed during a timed practice period. Write a proportion to find the distance the cyclist traveled in 30 min.
elapsed time   distance
10 min        3 mi
25 min        7.5 mi
Graph it. :)
Start at (0,0), then at 10 min. on the x-axis, go 3 spaces up on the y-axis and plot a point. Do the same for 25 min. and 7.5 miles. Draw a line through all of those points, and see where the line hits on the y-axis when the x-axis is at 30 min. :)
If two things vary directly it means their ratio is a constant.  Therefore from the formula rt=d. r=d/t,  r=3/10 or 7.5/25  which reduces to 3/10.  This is the constant speed,the lable is mi/min.  Now use  (d/30)=(3/10)  and solve for d.  Cross multiply and 10d=90, or d=9 mi
Using the information given, the distance formular = 0.3t ; distance covered in 30 minutes = 9 miles
Since the speed is constant :
We could use either of distance and elapsed time values to create an equation :
Elaspsed time - - - - Distance
10 minutes _____ 3 miles
Recall :
Distance covered = speed × time
Distance covered = speed × time Speed = distance / time
Speed of bicyclist is thus :
(3 miles / 10 minutes) = speed
Speed = 0.3 miles per minute
Hence,
Distance = 0.3 × time
For a travel time of 30 minutes ;
Distance covered = 0.3 × 30 = 9 miles
Hence, distance formular = 0.3t ; distance covered in 30 minutes = 9 miles
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