Probability

How likely something is to happen.

Many events can't be predicted with total certainty. The best we can say is how likely they are to happen, using the idea of probability.

Tossing a Coin 

When a coin is tossed, there are two possible outcomes:

• heads (H) or
• tails (T)

We say that the probability of the coin landing H is ½.

And the probability of the coin landing T is ½.

Example 1:

The chances of rolling a "4" with a die

Number of ways it can happen: 1 (there is only 1 face with a "4" on it)

Total number of outcomes: 6 (there are 6 faces altogether)

So the probability = 16

Example 2:

There are 5 marbles in a bag: 4 are blue, and 1 is red. What is the probability that a blue marble gets picked?

Number of ways it can happen: 4 (there are 4 blues)

Total number of outcomes: 5 (there are 5 marbles in total)

So the probability = 45 = 0.8

Example 3:

There are 7 marbles in a bag: 5 are blue, and 2 is red. What is the probability that a blue marble gets picked?

Number of ways it can happen: 2 (there are 2 blues)

Total number of outcomes: 7 (there are 7 marbles in total)

So the probability = 27

Exercise:

There are 6 flowers; 1 lavender, 2 roses and 3 sunflower. What is the probability of getting

(a) Lavender roses

(b) sunflower roses