Unit 2
4 marks · EasyA circle has a radius of 6 cm. Use the formula to calculate its circumference. Then, use your answer to work out the probability that a point chosen at random on the circle's circumference lies in the first quarter (a 90° arc).
Find the circumference of the circle. Use .
What is the probability that a randomly chosen point on the circumference lies in the first quarter (90°) of the circle? Give your answer as a fraction.
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) 37.68 cm · must show 2 × 3.14 × 6
(b) 1/4 · must show Recognises that a quarter of a circle corresponds to 90°/360° = 1/4
Also accept: 1/4
Common mistakes: Using diameter instead of radius; Not reducing the fraction
Show mark scheme and worked solution
Marking points
M1 (a) · 1 mark · Correct substitution into formula
A1 (a) · 1 mark · Accurate calculation: 37.68 cm
B1 (b) · 2 marks · Probability of first quarter = 1/4
Worked solution
a) C = 2 × 3.14 × 6 = 37.68 cm
b) First quarter is 90° out of 360°, so probability = 90/360 = 1/4.