PROBABILITY

1. What is the probability of1.1 getting heads when you throw a coin?

1.2 throwing a 1 on a dice?

HEADS TAILS

2

1

1 2 3 4 5 6

6

1

2. If I have 7 balloons at a party, 4 red and 3 yellow, and a blindfolded person has

to pop one, what is the probability that it will be a red one?

1 2 3 4 5 6 7

7

4

3. If there are 10 balloons at another party, 4 red, 3 yellowwhat are the chances that a red one will be popped first?

1 2 3 4 5 6 7

10

4

and 3 green,

8 9 10

4. At the heart, a box of smarties breaks open and 12 smarties fall on the floor,

(2 red, 3 green, 4 purple, 3 yellow). Mr Loubser is happy to eat off the floor, so he grabs for a smartie (as do a couple of other people who are also happy to eat off the floor).

What is the probability that the first one that is picked up is(i) red?(ii) purple?

12

2 4

5. I have 7 Chinese checkers.

Now for the PROBABILITY TREE:

4 red and 3 blue in a box.a. If I take one out, what is the probability of it being red?

R B4/7 3/7

b. If I take two out, what is the probability of BOTH being red?

R B3/6 3/6

3/6 x 4/7 = 12/42 = 2/7c. If I take two out, what is the probability of one red and one blue?

One red :

Two red :

3/6 x 4/7 = 12/42 = 2/7First red then blue :

R B4/6 2/6

The complete tree looks like:

RB3/6 x 4/7

12/42

RR3/6 x 4/712/42

BR4/6 x 3/7

12/42

BB2/6 x 3/7

6/42

4

7

4/7

3

6

3

6

4/6 x 3/7 = 12/42 = 2/7or first blue then red : Can be: first red then blue or first blue then red

Probability = 2/7 + 2/7 = 4/7

5/10

6. There is a lucky draw, based on the colour of the ticket you draw out of a box (Of course, the box is see through when you draw it. You get R50 if you draw a yellow ticket and R100 if you draw a green one).

In the box are 6 yellow ticketsand 5 green tickets.6.1 If you are allowed to take only 1 ticket, what is the probability of you

drawing a green ticket?

Y G6/11 5/11

Y G6/10 4/10

6.2 If you are allowed to take only two tickets from the box, what is the probability: (NB draw a tree diagram)

a. of drawing 2 green tickets?4/10 x 5/11 = 20/110 = 2/11Two

green : b. of drawing 1 yellow and 1 green ticket?

5/10 x 6/11 = 30/110 = 3/11Yellow then green :

Y G5/10

5/11

5/10 x 6/1130/110

YY5/10 x 6/11

30/110

6/10 x 5/11

30/110

4/10 x 5/11

20/110

The complete tree looks like: YG GY GG

6/10 x 5/11 = 30/110 = 3/11Or green then yellow :

One green :

Can be: first yellow then green or first green then yellowProbability = 3/11 + 3/11 = 6/11

7. There are 9 buttons in a box. 3 red, 4 white and 2 blue.Draw a tree diagram to determine the following:

a. What is the probability of taking a white button?b. If you are allowed to take 2 buttons, what is the

probability of their both being white?c. If you are allowed to take 2 buttons, what is the

probability of their being 2 different colours?

8. There are 12 cards in a pack, 4 jacks, 4 queens and 4 kings.

a. If you pick a card, what is the probability of picking a queen?

b. If you pick a second card, what is the probability of their both being queens? (Do a tree diagram)