Question

Elizabeth is 11 meters into the race after 4 seconds but is only 13 meters in after 12 seconds (her tricycle is slow because she has a flat tire). What is her speed (in unit rate)

Answer 1

First total number of meters = 11 meters.

First number of seconds = 4 seconds.

Second total number of meters = 13 meters.

Second number of seconds = 12 seconds.

Speed in unit rate = $\frac{Difference \ between \ distances\ }{Difference \ between \ times}$

Plugging values in the formula.

Speed in unit rate = $\frac{13-11}{12-4}$

= $\frac{2}{8}$

On dividing 2 by 8 , we get 0.25.

Therefore, speed is 0.25 meter per second.

Answer 2

From the information given in the question we can easily see that in the first four seconds the distance covered was 11 meters. So, Elizabeth's speed in the first 4 seconds of the race will be: $\frac{11}{4}=2.75 m/s$.

But her net speed will be the total distance of 13 meters divided by the total time of the race, which is 12 seconds.

Therefore, the net speed of Elizabeth's cycle will be: $\frac{13}{12}\approx 1.083$ meters per second.

We can also find the speed after the tire got flat as follows:

The distance travelled with the flat tire=13-11=2 meters

The time take with the flat tire=12-4=8 seconds

Therefore, the speed of Elizabeth's tricycle with the flat tire can be calculated as:

$\frac{2}{8}=0.25$ meter per second.

We have calculated all the three speeds.