Answer:
This probaly sounds a little confusing
Explanation:
1 day = 10 laps
1 lap = 400 meters
1 km = 1000 meters
12 km = ? days
We can use this information to find out a lot that we don't know.
HOW MANY METERS PER DAY??
In order to find the number of meters in a day, we think, "She ran 400 meters 10 times... 400 times 10... that's 4000 meters in one day."
1 day = 4000 meters (10 x 400 meters)
HOW MANY KILOMETERS PER DAY?
In order to find the number of km in a day, we can think, "One thousand is a kilo. There are 4 'one thousand's in 4000. Kali ran 4 kilometers (literally 4 thousand meters) per day.
1 day = 4 km (4000 m / 1000)
From here you can solve simply by thinking "How many 4km does it take to get to 12km?"
4 x ? = 12
? = 12 / 4
? = 3