Step by step
The question
Question: change 2 km² to square meters.
1 Change the length
This square is 1 kilometer on each side.
Its area is 1 square kilometer.
1 kilometer is 1,000 meters.
So each side is 1,000 meters long.
2 Change the area
So the square holds 1,000 rows of 1,000 small squares, each 1 square meter.
We draw only a few of them.
So 1 square kilometer is 1,000 meters times 1,000 meters.
1,000 times 1,000 is 1,000,000.
So 1 km² = 1,000,000 m².
Not 1,000: the 1,000 comes in twice.
3 Multiply
Each square kilometer is 1,000,000 square meters.
We have 2 of them, so we multiply: big unit to small unit.
Careful!
Times 1,000 only changes a length.
A square has two sides to change: times 1,000, and times 1,000 again.
Times 1,000,000: write 6 zeros after 2.
So 2 km² = 2,000,000 m².
4 Check
Let's check: go back the other way.
Divide by 1,000,000.
We get 2 square kilometers again.
So it is right!
Let's look back.
First: change the length.
Then: change the area.
Then: multiply.
Last: check.