Cambridge International Mathematics

biP(both boot up)

=P(DandL)

=0: 9 £ 0 : 7

=0: 63

ii P(desktop boots up but laptop does not)

=P(DandL^0 )

=0: 9 £ 0 : 3

=0: 27

Example 14 Self Tutor

Bag A contains 4 red jelly beans and 1 yellow jelly bean. Bag B contains 2 red

and 3 yellow jelly beans. A bag is randomly selected by tossing a coin, and one

jelly bean is removed from it. Determine the probability that it is yellow.

P(yellow)=P(A and Y)+P(B and Y)

=^12 £^15 +^12 £^35 fbranches markedXg

= 104

=^25

EXERCISE 25H

1 Suppose this spinner is spun twice: a Copy and complete the branches on the

tree diagram shown.

b What is the probability that blue appears on both spins?

c What is the probability that green appears on both spins?

d What is the probability that different colours appear on both spins?

e What is the probability that blue appears oneitherspin?

2 In a particular board game there are nine tiles: five are green and the

remainder are brown. The tiles start face down on the table so they

all look the same.

a If a player is required to pick a tile at random, determine the

probability that it is:

i green ii brown.

To get a yellow we take

either the first branch ticked

the second one ticked.

We the probabilities for

these outcomes.

or

add

4R 2R

1Y 3Y

Bag A Bag B R A and R

R B and R

A

Y A and YX

Y B and YX

B

(^4) –
5
(^2) –
5
(^1) –
2
(^1) –
2
(^1) –
5
(^3) –
5
ticket outcome
bag
B
Probability (Chapter 25) 523
IGCSE01
cyan magenta yellow black
(^05255075950525507595)
100 100
(^05255075950525507595)
100 100
Y:\HAESE\IGCSE01\IG01_25\523IGCSE01_25.CDR Monday, 27 October 2008 2:31:25 PM PETER