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Probability Problem solving Combined probabilities Relative Frequency Use two way tables to calculate probabilities The probability scale

Basic probabilities A bag contains 4 red, 5 blue and 6 yellow beads. One bead is chosen at random. Write down the probability of choosing a) a red bead b) a blue or yellow bead.

Basic probabilities Here is a fair 8-sided spinner. Jill is going to spin the spinner once. It will land on one of the colours. Which colour is the spinner most likely to land on? What is the probability that the spinner will land on the colour green? On the probability scale below, mark with a cross (x) the probability that the spinner will land on a green

Basic probabilities The spinner shown is spun. What is the probability that the arrow lands on   a) a prime number b) an odd number c) a square number? Give your answer as a fraction in lowest terms.

Probability- Your turn There are 10 red, 8 blue and 2 white balls in a bag. One ball is taken out of the bag.   a) Calculate the probability that the ball is red. b) Calculate the probability that the ball is blue. c) Calculate the probability that the ball is white. d) Which colour ball is most likely to be taken out? e) Which colour ball is least likely to be taken out? f) Calculate the probability that the ball is yellow. g) Calculate the probability that the ball is red, blue or white. h) Calculate the probability that the ball is not blue.

Probability- ANSWERS There are 10 red, 8 blue and 2 white balls in a bag. One ball is taken out of the bag.   a) Calculate the probability that the ball is red. b) Calculate the probability that the ball is blue. c) Calculate the probability that the ball is white. d) Which colour ball is most likely to be taken out? e) Which colour ball is least likely to be taken out? f) Calculate the probability that the ball is yellow. g) Calculate the probability that the ball is red, blue or white. h) Calculate the probability that the ball is not blue.

Now try section A from your work book

Calculating probabilities from a table A coin is tossed and a dice rolled. a) List, systematically, all the possible outcomes. b)What is the probability of getting a head and an odd number? c) What is the probability of getting an tail and a prime number?

Calculating probabilities from a table All of 10SC went abroad last year. This table shows where they went. a) Complete the table. b) One student is picked at random from the class. Write down the probability that the student i) visited America ii) is a girl who visited Europe   Europe America Rest of the world Total Girls 13 18 Boys 2 12 22 5

Calculating probabilities from two way tables – YOUR TURN One hundred shoppers are asked to name their favourite flavour of crisps. The results are shown in the two-way table. One shopper is selected at random. Calculate the probability that the person: a) is male b) is a male who prefers plain crisps c) is a female who prefers cheese and onion crisps   Plain Salt & Vinegar Cheese & onion Male 10 24 6 Female 25 15 20

Calculating probabilities from two way tables – YOUR TURN One hundred shoppers are asked to name their favourite flavour of crisps. The results are shown in the two-way table. One shopper is selected at random. Calculate the probability that the person: a) is male b) is a male who prefers plain crisps c) is a female who prefers cheese and onion crisps   Plain Salt & Vinegar Cheese & onion Male 10 24 6 Female 25 15 20

Now try section B from your work book

Relative frequency A school canteen offers four meal choices. Students can choose salad, pizza, meat pie or fish The table shows the probability that a student will choose salad or meat pie or fish One student is chosen at random from the students who are going to use the canteen. Work out the probability that the student (i) Chooses Meat Pie (ii) Chooses Salad OR fish (iii) Chooses Pizza Meal Salad Pizza Meat Pie Fish Probability 0.2   0.23 0.16

Probabilities add to 1 Four teams reach the semi-finals of a hockey competition. The probabilities of each team winning the final are given in this table. a) Explain how St. Patrick’s and St. Bartholomew’s chances of winning compare. b) Find the value of ‘p’. St Trinian’s St John’s St Bartholomew’s St. Patrick’s 0.35 0.25 p 3p

Exam style questions A bag is filled with 40 coloured balls. 15 of the balls are red. The probability that a ball picked at random is red or green is 0.7. How many green balls are in the bag?

Exam style questions- Your turn Peter picks a playing card at random from a normal pack of playing cards. The jokers have already been removed. Find the probability of each of these results. (Write your answers as fractions cancelled to their lowest terms, there are 52 cards in a pack.) a) He picks a Heart b) He picks an Ace c) He doesn’t pick a ‘Picture card’ d) He picks a 10 or a Jack. e) He picks the Ace of Spades

Now try section C from your work book