Handling Data 7
3 marks · Easy(a)[1 mark]
A bag contains 2 white balls and 4 black balls. One ball is picked at random (without replacement), then a second ball is picked. Write down the probability that the first ball picked is white.
(b)[2 marks]
Calculate the probability that both balls picked are black.
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) 1/3
(b) 2/5
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly states probability for first ball is white: 2/6 or 1/3
M1 (b) · 1 mark · Multiplies probabilities for no replacement: 4/6 × 3/5
A1 (b) · 1 mark · Finds correct probability: 2/5 or 0.4
Worked solution
a) Probability first is white = 2 white / 6 balls = 1/3