Probability = $\frac{\mathrm{Number\; of\; possible\; selection}}{\mathrm{Number\; of\; samples}}$

Number of good oranges = 20 - 6 = 14

Number of samples = 20

Probability (Good oranges) = $\frac{14}{20}$ = $\frac{7}{10}$

Note: 2 divides 14, 7 times and 20, 10 times.

Samples = {1,2,3,4,5,6}

Number of samples = 6

Samples of numbers greater than 5 = {6}

Number of samples of number greater than 5 = 1

Probability = 1/6

5 red

7 black

ASSIGNMENT

What’s the propability of picking a red ball?

NOTE: When you sum all the probabilities, you are supposed to get 1

Concept

Probability = No. of possible outcomes / No. of sample space

No. of sample space (Total numbers in the set or under examination) = 12

We have to list the prime numbers of the set p and count them to get the No. of possible outcomes

A prime is a number that is greater than 1 and divisible only by itself and 1 (e.g. 2, 3, 5, 7, 11,...)

Note: 1 is not a prime number

⇒ the prime numbers from the set p are {2,3,5,7,11}

The total possible prime numbers is 5 (when you count the list of prime numbers above, you are to get 5)

⇒ The probability of selecting a prime number = 5 / 12

What will the probability of selecting i)an even number ii) old number?

i) Probability of selecting an even number

An even number is a number divisible by 2

Hence the even numbers from set p are {2,4,6,8,10,12} which when you count you will get 6

⇒ The probability of selecting an even number = 6 / 12 = 1/2

ii) Probability of selecting an odd number

Odd numbers are whole numbers that cannot be divided exactly into pairs. Odd numbers, when divided by 2, leave a remainder of 1.

Hence the odd numbers from set p are {1,3,5,7,9,11} which when you count you will get 6

⇒ The probability of selecting an odd number = 6 / 12 = 1/2

5 red

7 black

ASSIGNMENT

What’s the propability of picking a red ball?

NOTE: When you sum all the probabilities, you are supposed to get 1

Number of letters = 5

Number of P in HAPPY = 2

P(P) = $\frac{2}{5}$

P = {1, 2, 3, 4, 5, ... 10}

P = {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

Total number of numbers (samples) = 10

Set of numbers greater than 3 = {4, 5, 6, 7, 8, 9, 10}

Number of numbers greater than 3 (Possible selection) = 7

P(>3) = $\frac{7}{10}$