Theresa ran on a treadmill for thirty minutes, and her time and speed are shown on the graph above. According to the graph, which of the following statements is NOT true concerning Theresa’s run?

The correct answer is: Theresa’s speed was increasing for a longer period of time than it was decreasing.

HINT – Observe the graph and statements given in the options closely and then choose the FALSE statement
SOLUTION – For A) We can see that graph is parallel to x – axis when time varies from 5 mins to 10 mins.
y – coordinate is constant when x = 5 to x =10
Speed is constant for five minutes.           ( 10 – 5 = 5 mins)
So, statement A is true
For C)
We can see that for the last 5 mins graph is a straight line.
Slope of the graph is constant
Rate of change of the speed is constant
We know that rate of change is given by slope of the graph. And since the line on the graph falls.
Slope is negative
Hence, speed is decreasing at a constant rate for the last 5 mins
So, statement C is true
For D)
The last 10 mins means x = 20 to x = 30. We can observe that when
x = 25, y = 8 i.e. highest point
So, speed reached its maximum at 25 mins
Hence, statement D  is true
For B)
We can observe that the line on the graph is moving upward from left to right from x = 0 to x = 5 and then from x = 20 to x = 25
Slope is positive from x = 0 to x = 5 and x = 20 to x = 25
Speed is increasing for 10 mins
But the line on the graph is moving downward from left to right from x = 10 to x = 20 and then from x = 25 to x = 30
Slope is negative from x = 10 to x = 20 and x = 25 to x = 30
Speed is decreasing for 15 mins
Hence, speed is decreasing for longer period of time
So, statement B is false
Hence, option B is correct