The distance of 1 lap around the school track is 400 meters. If a student runs 8 laps how many kilometers has the student run?

Question

The distance of 1 lap around the school track is 400 meters. If a student runs 8 laps how many kilometers has the student run?

A) 3.2

B) 32

C) 3200

D) 3,000,200

Answer 1

Cassandra,

400 meters x 8 laps = 3,200 meters.

Divide 3,200 meters by 1,000 to convert to kilometers.

The answer is 3.2

Answer 2

1 lap = 400 meters

Therefore, we can use something called "dimensional analysis" to convert from laps to meters. We use equivalent quantities to do so. Since 1 lap = 400 meters, we can say

1 = 400 meters / 1 lap.

This gives us a "conversion factor" between laps and meters. Since we know we have traveled 8 laps, we can multiply this by our conversion factor (which we have defined to be equal to 1!):

8 laps * 1 = 8 laps * 400 meters / 1 lap

Now we can cancel words the same way we cancel numbers in a fraction. If we have 4 / 4, we cancel the 4's and get 1. Similarly, in the above we can cancel the "lap" with the "lap" on the bottom of the fraction of the conversion factor. Then we have:

8 laps = 3200 meters

Giving a final answer.

Let me know if this doesn't make sense!