UR

Probability of independent events

Amal

A number cube is rolled and a coin is tossed. The number cube and the coin are fair. What is the probability that the number rolled is less than 3 and the coin -

toss is tails?

Write your answer as a fraction in simplest form.

8

Probability for either side of a fair coin: 1/2. A coin has two sides.

Probability of any side of a dice: 1/6. A cube has 6 sides.

P (number rolled on dice is less than 3: 1/6 + 1/6 = 2/6 = 1/3.

Why do we add 1/6 two times? On a cube there are 2 numbers less than 3. You know the numbers to be 1 and 2.

P (Coin is heads) : 1/2

P (Coin is heads AND dice is less than 3) : 1/3 x 1/2 = 1/6.

Understand?