Key Stage 3
Single Event Probability
When calculating single event probability:
- First find all possible outcomes that fit the description
- Count how many outcomes there are
- Write it as a probability
- Simplify your answer whenever possible
For example, to solve question 1:
- All possible odd outcomes: 1,3,5,7 (
- That makes 4 outcomes
- So 4/8
- Simplify it to ½
- There are 8 counters in a box numbered 1, 2, 3, 4, 5, 6, 7 and 8. If one counter is drawn out at random, what is the probability that it is a counter:-
- with an odd number, b) with an even number,
- with a square number, d) that is greater than or equal to 6?
- I have a pack of playing cards, containing 52 cards. I pick a card at random. What is the probability that the card I select is:-
- a king, b) a diamond,
- a black card, d) the jack of clubs?
- There are four different coloured writing pads. In a pack there are three blue, eight red, one white and four green. What is the probability when I open a new pack I randomly pick a :-
- blue pad, b) red pad, c) white pad,
- green pad, e) yellow pad, f) red or green pad?
- Draw the number line in your book. The number line represents all possibilities. Indicate, by arrows labelled “a” to “f” the probabilities for :-
a) throwing a tail on a coin, b) cutting a diamond from a pack of a cards,
c) saturday following friday, d) the water being cut off today,
e) scoring a 2 or a 3 on a dice, f) your teacher becoming a dinosaur.
5) Arrange these events in order of which is “most likely” down to which is “least likely”:-
a) throwing a dice and getting a “1”.
b) being born on a day with “y” in it.
c) spinning a coin and it landing on a tail.
d) somebody having their birthday on New Year’s Day.
6) Arrange these events in order of which is “most likely” down to which is “least likely”:-
a) picking a red card from a pack of cards.
b) a fair 4 sided spinner labelled 1, 2, 3, and 4 landing on 4.
c) eating a meal some time this month.
d) winning the jackpot of the National Lottery.
7) A biased coin has a probability of landing on heads of 0.6. What is the probability of landing
8) Another biased coin has a probability of landing on tails of 0.35. What is the probability of
landing on heads?
9) Year 9 and Year 10 boys play a football match with a penalty shoot-out, so the teams cannot draw. The probability of Year 9 winning is 0.42, what is the probability of Year 10 boys winning?
10) Year 7 and Year 8 girls play a netball match with a penalty shoot-out, so the teams cannot draw. The probability of Year 8 winning is 0.76, what is the probability of Year 7 winning?
11) Ben plays a game of chess against a computer, it cannot draw. The computer is set to have a 0.57 chance of winning the game. What is the probability that Ben wins the game?
Below are some useful websites.
Highly recommended is myimaths.com.
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