Question 1: If the radius of a circle is 7 cm, calculate its diameter.

Answer: 14 cm

Question 2: A circle has a diameter of 20 meters. What is its radius?

Answer: 10 meters

Question 3: Calculate the diameter of a circle with a circumference of 31.4 meters. (Use π ≈ 3.14)

Answer: 10 meters

Question 4: Construct a circle on the grid with a diameter of 6 cm. Use a ruler for accuracy.

Answer: Student draws the circle with 6cm diameter

Question 5: A bike wheel has a diameter of 70 cm. How far does the wheel travel in one full rotation? (Circumference = π×diameter, π ≈ 3.14)

Answer: 219.8 cm

Question 6: A circular garden has a radius of 5 meters. Find its diameter.

Answer: 10 meters

Question 7: A circular pool has a diameter of 12 meters. What is its radius?

Answer: 6 meters

Question 8: A wheel with a diameter of 0.5 meters rolls forward. How many meters does it cover in 10 revolutions?

Answer: 15.7 meters

Question 9: A circular track has a diameter of 400 meters. Calculate its circumference.

Answer: 1256 meters

Question 10: Identify and correct the mistake: A student calculates the diameter of a circle as 8 cm, having measured the radius as 4 cm.

Answer: No mistake; diameter = 2×radius = 8 cm. Student's calculation is correct.

Question 11: A circular fountain has a diameter of 15 meters. If the diameter increases by 2 meters, what is the new diameter?

Answer: 17 meters

Question 12: Explain why the diameter of a circle is always twice its radius. Use the circle's properties in your explanation.

Answer: Because by definition, the diameter passes through the center and touches two points on the circle's edge, making it twice the length of the radius, which is from the center to any point on the circle.