Kali trains for a race by running around a track. each lap around the track is 400 meters. she runs 4 kilometers each day. how many laps around the track does kali run in 3 days?

First step, is to work out how many laps she runs in 1 day.
To do this, we divide what she runs in one day, by the length of one lap
4km / 400m
TO make this easier, we change to units of one number to make them both the same
We will turn them both into meters
4km = 4000m (1km is equal to 1000m, therefore we multiply by 1000)

4000/400 = 10 laps per day

Now we want to find out how many laps are completed in 3 days
If 1 day is equal to 10 laps and we want 3 days, we multiply 10 laps by 3 days
10 x 3 = 30 laps

Kali runs 30 laps in 3 days