Provide properties of a parallelogram, rhombus, and trapezoid, and solve problems involving the area of a square and probability.

The area of a square is given by $A = s^2$, where $s$ is the side length.

The area of the square is $\boxed{\text{81 cm}^2}$.

3. What is the probability of picking a red ball from a bag with 3 red balls and 2 blue balls.

Number of red balls = 3
Number of blue balls = 2
Total number of balls = $3 + 2 = 5$

Probability of picking a red ball = $\frac{\text{Number of red balls}}{\text{Total number of balls}}$

The probability of picking a red ball is $\boxed{\frac{3}{5}}$.

4. A coin is flipped. What is the chance it lands on heads.

The possible outcomes are Heads (H) or Tails (T). There are 2 possible outcomes.

There is 1 favorable outcome (Heads).

Probability of landing on heads = $\frac{\text{Number of favorable outcomes}}{\text{Total number of outcomes}}$

The chance of landing on heads is $\boxed{\frac{1}{2}}$.

5. What is the place value of 7 in 3,745.

The digits are 3 (thousands place), 7 (hundreds place), 4 (tens place), and 5 (ones place).

The digit 7 is in the hundreds place.
The place value of 7 is $7 \times 100 = 700$.
The place value of 7 in 3,745 is $\boxed{\text{Hundreds (or 700)}}$.

6. Find the perimeter of a rectangle with length 8cm and width 5cm.

The perimeter of a rectangle is given by $P = 2(l + w)$, where $l$ is the length and $w$ is the width.

The perimeter of the rectangle is $\boxed{\text{26 cm}}$.

7. Convert 3.7kg to grams.

$1 \text{ kg} = 1000 \text{ g}$

$3.7 \text{ kg}$ is equal to $\boxed{\text{3700 g}}$.