Remember that a square is a rectangle with four equal sides.  

1. If a square has an area of $81$ square units, how long is each side?

   Hint (a):

   Take the square root of the area to find the length of each side.

2. Find the length of the side of a square with area $225$ square units.

   Hint (b):

   Use the same strategy as part (a).

3. Find the length of the side of a square with area $10$ square units.

   Hint (c):

   Use the same strategy as part (a).

   Answer (c):

   $\sqrt {10} \text{ units}$

4. Find the area of a square with side $11$ units.

   Hint (d):

   $\text{Area} = \left(\text{length}\right) \left(\text{width}\right)$