On an altitude-versus-time graph, the slope is the change in altitude divided by the change in time. Read two exact points, then use Desmos to evaluate that fraction. A falling line has a negative rate; read the axis labels rather than treating every grid box as one unit.
Hints
- Hint 1
A marked point gives a time first and an altitude second. Read each value from the labeled axes, not by counting boxes. What two time-altitude pairs do the dots show?
- Hint 2
The slope puts altitude change over time change. Subtract the altitudes in the same order as the times, so your result keeps the sign of the descending line.
Step-by-step
Find the rate from two points
Step 1Read the marked points
The dots show and : after minute the balloon is at meters, and after minutes it's at meters. Each vertical tick is 10 meters, not meter. The line falls as time increases, so expect a negative rate.
- Step 2
Put altitude change over time change
The slope gives the altitude change per minute. Subtract the second altitude minus the first, and do the same with the times:
Keeping the subtractions in the same order preserves the direction of the change.
- Step 3
Evaluate and interpret the rate
Type into Desmos. It displays . The rate is the signed altitude change per minute, not the entire drop between the dots. The balloon's altitude changes at meters per minute, meaning it loses meters each minute. Choice B.