Let's solve the problems given in the image:

Problem 2:

• The radius of the circle is $r = 3 \, \text{cm}$.
• Use $\pi \approx 3.14$.
• Circumference formula:
  $\text{Circumference} = 2 \pi r$
  Substituting the values:
  $\text{Circumference} = 2 \times 3.14 \times 3 = 18.84 \, \text{cm}$

Problem 4:

• The radius of the circle is $r = 7 \, \text{cm}$.
• Use $\pi \approx \frac{22}{7}$.
• Circumference formula:
  $\text{Circumference} = 2 \pi r$
  Substituting the values:
  $\text{Circumference} = 2 \times \frac{22}{7} \times 7$
  The 7 in the numerator and denominator cancel out:
  $\text{Circumference} = 2 \times 22 = 44 \, \text{cm}$

Summary of answers:

1. For the first circle (radius = 3 cm), the circumference is 18.84 cm.
2. For the second circle (radius = 7 cm), the circumference is 44 cm.

Do you want further explanation or details? Here are five related questions to deepen your understanding:

1. What is the formula for calculating the area of a circle, and how would you use it for these examples?
2. How does the choice of different approximations for $\pi$ affect the results?
3. Can you derive the formula for circumference from the definition of $\pi$?
4. What would be the circumference of a circle with radius 5 cm using both $3.14$ and $\frac{22}{7}$ for $\pi$?
5. Why is $\pi$ often approximated as both $3.14$ and $\frac{22}{7}$?

Tip: Always ensure to use the same value of $\pi$ throughout your calculations to avoid inconsistencies!