Section 1 - Area and Circumference of a circle Flashcards
What is the formula for the circumference of a circle?
C = 2πr
What is the formula for the area of a circle?
A = πr²
True or False: The diameter of a circle is twice the radius.
True
If the radius of a circle is 5 cm, what is its circumference?
31.4 cm
If the diameter of a circle is 10 cm, what is its radius?
5 cm
Fill in the blank: The circumference of a circle can also be calculated using the formula C = ______.
πd
What is the area of a circle with a radius of 7 cm?
153.94 cm²
Multiple Choice: What is the value of π (pi) approximately?
3.14
What is the relationship between the radius and diameter of a circle?
Diameter is twice the radius.
True or False: The area of a circle increases as the radius increases.
True
If the circumference of a circle is 62.8 cm, what is the radius?
10 cm
Fill in the blank: The radius is ______ of the diameter.
half
What unit is commonly used to measure the area of a circle?
Square units (e.g., cm²)
If the area of a circle is 78.5 cm², what is its radius?
5 cm
Multiple Choice: Which of the following is NOT a formula for the circumference of a circle? A) C = 2πr B) C = πd C) C = r²
C) C = r²
What happens to the area of a circle if the radius is doubled?
The area increases by a factor of four.
True or False: The circumference of a circle can be calculated without knowing the radius.
True, if the diameter is known.
What is the circumference of a circle with a radius of 3 cm?
18.84 cm
If the diameter of a circle is 12 cm, what is its area?
113.1 cm²
Fill in the blank: The area of a circle is proportional to the ______ of its radius.
square
What is the formula to calculate the diameter if you know the circumference?
d = C/π
Multiple Choice: Which formula would you use to find the area of a circle? A) A = 2πr B) A = πr² C) A = πd
B) A = πr²
If the radius of a circle is increased by 1 cm, how does that affect the circumference?
It increases by 2π cm.
What is the area of a circle with a diameter of 10 cm?
78.5 cm²
True or False: The units for circumference are the same as those for the diameter.
True
If a circle has an area of 314 cm², what is its radius?
10 cm
Fill in the blank: The circumference of a circle can be found using the formula C = ______.
2πr or πd
What is the relationship between the area and the radius of a circle?
Area increases with the square of the radius.
If the radius of a circle is halved, what happens to the area?
The area is reduced to one fourth.
Multiple Choice: Which of the following is the correct formula for the area of a circle? A) A = πd B) A = 2πr C) A = πr²
C) A = πr²
What is the circumference of a circle with a radius of 4 cm?
25.12 cm
