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

Answer: 14

Question 2: A circle has a diameter of 18 m. What is its radius?

Answer: 9

Question 3: Calculate the circumference of a circle with diameter 10 cm. Use π ≈ 3.14.

Answer: 31.4

Question 4: A circle's radius is increased from 5 cm to 8 cm. What is the new diameter?

Answer: 16

Question 5: Plot the graph of y=2x on the grid. What is the diameter of the circle with radius 4 cm if the diameter is proportional to the value of y?

Answer: 8

Question 6: Construct a triangle with sides 6 cm, 8 cm, and a diameter of the circle. Show that the diameter is the longest side.

Answer: The diameter (longest side) is 10 cm, which makes the triangle valid by the triangle inequality.

Question 7: A pipeline forms a circle of diameter 12 meters. How much pipe is needed to go all the way around?

Answer: 37.68

Question 8: Identify and correct the mistake in the following statement: 'The diameter of a circle is equal to its radius.'

Answer: The diameter is twice the radius, not equal.

Question 9: A circle has a diameter of 24 cm. If a chord is drawn parallel to the diameter and measures 16 cm, can this chord be the diameter? Explain.

Answer: No, because the diameter is 24 cm and the chord is only 16 cm; they are different segments.

Question 10: Calculate the diameter of a circle if the area is 78.5 cm². (Use π ≈ 3.14)

Answer: 10

Question 11: Explain why the diameter always passes through the center of the circle and how it relates to the radius.

Answer: The diameter passes through the center because it is the longest chord, and it is twice the radius.