Solution Mathematics 4024

(a) A bag contains 40 balls.
28 of the balls are red and the rest are green.
Aisha takes a ball from the bag at random, notes its colour and replaces it.
(i) Find the probability that this ball is green.
................................................. [1]
(ii) Aisha repeats this 200 times.
Work out the number of times she expects to take a green ball.
................................................. [1]
(b) A bag contains 9 blue balls and 7 yellow balls.
Sergio takes two balls from the bag at random without replacement.
(i) Complete the tree diagram.
blue
First ball Second ball
yellow
blue
yellow
blue
.........
.........
.........
.........
yellow
16
9
15
8
[2]
(ii) Find the probability that the two balls are the same colour.
................................................. [2]