Answer:
the zero property
Step-by-step explanation:
Do they know how to divide?
If so, tell them to divide the number in as many ways until you go past the number
For example, if your seeing if 9 is a prime number divide 9 by ,1,2,3,4,5,6,7,8,9 and only count the whole numbers.
This sounds complicated so just teach them simple time tables
Check the picture below.
notice, is just a circle inscribed in a square.
now for the first one, we know the diameter is 14, so the square is a 14x14, and the radius of that is half the diameter or 7.
now, if we get the area of the square, which includes the area of the circle, and THEN get the area of the circle and subtract it from the square's, what's leftover is the shaded section.

now, for the one on the right-hand-side, the radius is 8, and square's area is 16x16,