Circle area equation is 3.14 x r squared.
So for question 1,
The radius is 3 cm.
We can square the radius ( 3 squared = 9).
After that, 9 x 3.14 = 28.26.
And after that we match our answers on the right hand column. Since we don't have the answer as given, we try to look for similar numbers. If we look at H, it shows us 0.2826 km squared. When cm is turned into km, the decimal moves two digits to its left. So for question 1, H is correct.