GCSE Secondary Maths Age 13-17 - Probability & Statistics: Probability - Explained

The video tutorial explains how to calculate probabilities using a table of pen colors. It covers determining the number of black pens by multiplying the total number of pens by the probability of selecting a black pen. It also demonstrates finding the probability of selecting a green pen by subtracting the sum of other probabilities from one. The tutorial emphasizes that probabilities can be expressed as percentages, fractions, or decimals, but not as ratios.

If the probability of picking a black pen is 0.3, how many black pens are there in a box of 200 pens?

• 120

• 90

• 30

• 60

How many marks are awarded for correctly calculating the number of black pens?

• Four marks

• One mark

• Two marks

• Three marks

What is the probability of selecting a green pen if the probabilities of black, blue, and red pens are 0.3, 0.2, and 0.4 respectively?

• 0.1

• 0.3

• 0.4

• 0.2

If the total probability must equal 1, what is the missing probability if black, blue, and red pens have probabilities of 0.3, 0.2, and 0.4?

• 0.2

• 0.15

• 0.05

• 0.1

Which of the following is NOT a valid way to express probability?

• As a ratio

• As a decimal

• As a fraction

• As a percentage