KS3 Questions Probability. Level 3 to 5. 1. A survey was carried out on the shoe size of 25 men. The results of the survey were as follows: 5 Complete the tally chart and frequency table for this data. Size Tally Frequency 5 (b) One of the men is chosen at random. What is the probability that he has shoe size? (Total 3 marks) 2. The probabilities of the following events have been marked on the probability scale below. A: The next person to pass you will be less than 0 years old. B: Tomorrow will be Sunday. C: A fair three-sided spinner, coloured red, blue and green, will land on red. 0 1 Label each arrow with a letter to show which event it represents. (Total 2 marks)
3. Two bags, A and B, each contain four numbered discs that are all the same size. Bag A Bag B A disc is drawn at random from bag A and a disc is drawn at random from bag B. A score is obtained by adding the numbers on the two discs. Complete the table to show all the possible scores. Bag A + 1 3 5 2 3 5 Bag B 4 (b) Find the probability of scoring less than.. Answer... (Total 4 marks) 4. A box of chocolates contains soft centres, 5 toffee centres and nut centres. Mary chooses a chocolate at random. What is the probability that she chooses a chocolate with a toffee centre? Answer... (b) In a bag of sweets the probability of choosing a sweet with a soft centre is 0.4 What is the probability of choosing a sweet that does not have a soft centre? Answer... (Total 3 marks)
5. A bag contains blue, red and green cards only. One card is taken at random from the bag. The table shows the probabilities of taking a blue card and a red card. Colour Blue Red Green Probability 0.3 0.5 What is the probability of taking a yellow card from the bag? Answer... (b) What is the probability of taking a card that is not blue from the bag? Answer... (c) Complete the table to show the probability of taking a green card from the bag. (Total 3 marks) Level to.. A bag contains 12 blue and green counters. More blue and green counters are added to the bag such that for every blue counter added, two green counters are added. 1 The probability that a counter taken at random is blue is now 2 How many blue and green counters were added to the bag?............... Answer... blue... green (Total 2 marks)
. Gemma has a box of red, blue and green pencils. She chooses a pencil at random. The probability that she chooses a red pencil is 0.5 The probability that she chooses a blue pencil is 0.2 What is the probability that Gemma chooses a green pencil?... Answer..... (b) There were ten pencils in the box originally. How many pencils were green?.... A dice is suspected of bias. Here are the results of 20 throws. Answer..... (Total 4 marks) 3 4 2 3 1 5 2 4 3 4 3 1 1 2 5 5 3 Use these results to calculate the relative frequency of each score. Score 1 2 3 4 5 Relative frequency
(b) Use the relative frequency to calculate how many times you would expect to score 3 in 0 throws of this dice. Answer... (c) Compare your answer to part (b) with the number of times you would expect to score 3 in 0 throws of a fair dice.. Three cards are numbered 1, 3 and 4. Three discs are numbered 2, 4 and 5. (Total 5 marks) 1 3 4 21 4 5 A game consists of picking one card at random and one disc at random. The numbers on the card and disc are added together. (i) Complete the table to show all the possible totals. Disc 2 4 5 Card 1 3 3 4 (ii) What is the probability of getting a total which is an even number?.......... Answer...
(b) In a different game the probability of getting a total which is an even number is 3. 5 What is the probability of getting a total which is an odd number?........... Penny, Sam and Robert do this experiment on the same bag of counters. 1. Take a counter from the bag at random. 2. Record its colour. 3. Put the counter back in the bag. Repeat this trial a number of times. Answer... (Total 5 marks) Their results are shown in this table. Name of Number Colour of counter pupil of trials Black White Green Penny 0 4 Sam 40 3 1 21 Robert 200 22 2 Estimate the number of each different coloured counter in the bag. Clearly state the set of results that you use to make the estimate. Give a reason for your choice................ Set of results used... Reason...... Answer Black..., White..., Green. (Total 4 marks)