standard_description: Derive using similarity the fact that the length of the arc intercepted by an angle is proportional to the radius, and define the radian measure of the angle as the constant of proportionality; derive the formula for the area of a sector.
problem_activity: Task
Angel and Jayden were at track practice. The track is $\frac25$ kilometers around.
Angel ran 1 lap in 2 minutes.
Jayden ran 3 laps in 5 minutes.
How many minutes does it take Angel to run one kilometer? What about Jayden?
How far does Angel run in one minute? What about Jayden?
Who is running faster? Explain your reasoning.


aligns: no