## Probability Exercise

1. Ten disks are numbered from 1 to 10 and placed in a bag. If disks are randomly drawn from the bag, what is the probability that:

a. The number on the disk is odd?
b. The number of the disk is a multiple of 3?
c. The number on the disk is an odd number and a multiple of 5?
d. The number on the disk is an odd number or a multiple of 5?

2. A bag contains 6 white balls and 2 red balls. A student takes a ball from the bag.

What is the probability that the ball is:

(a) White?
(b) Red?
(c) Green?

3. A bag contains three red balls, four blue balls and five green balls. If two balls are drawn, with replacement, what is the probability that:

a. The first ball will be green?
b. The first ball is red and the second ball is blue?
c. Both balls are red?
d. Both balls are not green?

4. Repeat question 3 without the ball being replaced after the first draw.

5. A die is thrown and a coin is tossed. What is the probability of:

a. Throwing a five and tossing a head?
b. Scoring an even number on the die?
c. Getting an odd number on the die and tossing a tail?
d. Throwing a number less than a three and tossing a head?

6. Three fair coins are tossed. One side is called "heads" and the other side is called "tails". Draw a tree diagram to show all of the possible combinations and use the diagram to find the probability that:

a. All three coins are tails.
b. There are two heads and a tail (in any order).
c. There are no tails.
d. The first coins is a tail.

7. In a town, five out of eight children do not own a bicycle. If there are 2000 children in the town, how many would you expect to own a bicycle?

8. A die is rolled 60 times. How many times would you expect to throw:

(a) a 5 or a 6?
(b) an even number?
(c) numbers less than 5?

9. A die is rolled twice and the total is noted. Find the probability of getting:

(a) Two fours.
(b) A total of 7.
(c) A double.

10. A company buys three brands of computers: Brand A (40%) , Brand B (25%) and Brand C(35%).

Brand A have a 20% probability of developing a fault in the first year, Brand B 10% and Brand C 5%.

Draw a tree diagram to show this situation and find the probability that a computer will develop a fault in its first year.