Arc lengths and sectors
3 exam-style questions. Answers and the mark for each step are on the last page.
- Question 1
A round pizza has a diameter of 30 cm. It is cut into 8 equal slices from the centre.
(a) Work out the area of one slice. Give your answer correct to 3 significant figures.
- Question 2
A sector has angle and area cm².
(a) Find the radius of the sector.
(b) Find the exact arc length of the sector.
- Question 3
A sector of a circle has radius 6 cm. The area of the sector is .
(a) Work out the angle .
(b) Work out the perimeter of the sector. Give your answer in the form .
(c) The sector is folded so that meets , making a cone with no base. Work out the radius of the base of the cone.
Answers and marks
Question 1
(a)
- P1 The whole area with radius 15.
- P1 Dividing by 8 (or multiplying by ).
- A1 (awrt 88.4).
Question 2
(a) cm
- M1 Write the sector area as a fraction of πr².
- A1 Correct answer: cm
(b)
- M1 Take the same fraction of the circumference.
- A1 Correct answer:
Question 3
(a)
- P1 Setting up .
- A1 Correct answer: .
(b) cm
- M1 Arc length .
- A1 Correct answer: .
(c) 2.5 cm
- P1 Recognising that the arc length equals the base circumference.
- A1 Correct answer: 2.5 cm.