GCSE Exam Questions on Basic Probability. Richard has a box of toy cars. Each car is red or blue or white. 3 of the cars are red. 4 of the cars are blue. of the cars are white. Richard chooses one car at random from the box. Write down the probability that Richard will choose a blue car.. Here is a fair 4-sided spinner. 4 6 8 The spinner has four sections numbered, 4, 6 and 8. The spinner is to be spun. It will land on one of the sections. On the probability scale below mark, with a letter, the probability that the spinner will land (i) (ii) (iii) on (use the letter A), on an odd number (use the letter B), on a number greater than 3 (use the letter C). 0 (Total 3 marks) LILIAN BAYLIS TECHNOLOGY SCHOOL
3. Michael picks one number from Box A. He then picks one number from Box B. Box A 7 5 4 Box B 6 8 List all the pairs of numbers he could pick. One pair (, ) is shown. (, ).............. 4. Mr Brown chooses one book from the library each week. He chooses a crime novel or a horror story or a non-fiction book. The probability that he chooses a horror story is 0.4 The probability that he chooses a non-fiction book is 0.5 Work out the probability that Mr Brown chooses a crime novel.. 5. Mark throws a fair coin. He gets a Head. Mark's sister then throws the same coin. (a) What is the probability that she will get a Head? Mark throws the coin 30 times.... () (b) Explain why he may not get exactly 5 Heads and 5 Tails....... () LILIAN BAYLIS TECHNOLOGY SCHOOL
6. A box contains sweets which are red or green or yellow or orange. The probability of taking a sweet of a particular colour at random is shown in the table. Colour Red Green Yellow Orange Probability 0.5 0. 0.3 Sarah is going to take one sweet at random from the box. Work out the probability that Sarah will take an orange sweet.... 7. A train can be on time or early or late. The probability that the train will be on time is 0.69 The probability that the train will be early is 0.07 Work out the probability that the train will be late.. 8. A bag contains some sweets. The flavours of the sweets are either strawberry or chocolate or mint or orange. Sarah is going to take one sweet at random from the bag. The table shows the probability that Sarah will take a strawberry sweet or a mint sweet or an orange sweet. Flavour Strawberry Chocolate Mint Orange Probability 0.3 0.7 0. Work out the probability that Sarah will take a chocolate sweet.... LILIAN BAYLIS TECHNOLOGY SCHOOL 3
9. A bag contains some balls which are red or blue or green or black. Yvonne is going to take one ball at random from the bag. The table shows each of the probabilities that Yvonne will take a red ball or a blue ball or a black ball. Colour Red Blue Green Black Probability 0.3 0.7 0.4 Work out the probability that Yvonne will take a green ball.... 0. A box contains bricks which are orange or blue or brown or yellow. Duncan is going to choose one brick at random from the box. The table shows each of the probabilities that Duncan will choose an orange brick or a brown brick or a yellow brick. Colour Orange Blue Brown Yellow Probability 0.35 0.4 0.9 Work out the probability that Duncan will choose a blue brick.. The probability that a biased dice will land on a four is 0. Pam is going to roll the dice 00 times. (a) Work out an estimate for the number of times the dice will land on a four.... LILIAN BAYLIS TECHNOLOGY SCHOOL 4
. Twenty students took a short test. The test was marked out of 5. Their results are shown in the table below. Mark 0 3 4 5 Number of Students 3 5 4 5 (a) Write down the probability that a student chosen at random scores in the test. (b). Write down the probability that a student chosen at random scores 3 or more in the test. () () (Total 3 marks) LILIAN BAYLIS TECHNOLOGY SCHOOL 5
A SWERS. (i) A at ¼ 3 B for A halfway between 0 and ½ (ii) B at 0 (iii) C at ¾ B for C halfway between ½ and [3]. 4 9 3 + 4 + M for denominator of 9 or 4 in 9 or 4 out of 9 ( OT 4 : 9) A 3. (,) (,4) (,6) (,8) (5,) (5,4) (5,6) (5,8) (7,) (7,4) (7,6) (7,8) B for 8 correct pairs (i.e. 7 extra) B for all pairs, or all 4 pairs 4. 0.45 0.4 + 0.5 0.55 M for sum A for 0.45 o.e. SC B for 0.8 5. (a) (b) reason B for reason e.g could get 30 heads LILIAN BAYLIS TECHNOLOGY SCHOOL 6
6. 0.35oe (0.5 + 0. + 0.3) 7. 0.4 oe (0.69 + 0.07) 8. 0.3 (0.3 + 0.7 + 0.) 9. 0.9 (0.3 + 0.7 + 0.4) M for (0.3 + 0.7 + 0.4) A cao (SC: B for 0.56 seen) 0. 0. oe (0.35 + 0.4 + 0.9) 0.78. 40 00 0. 40 M for 00 0. or seen 00 A for 40. (a) /0 (b) /0 4 + 5+ 0 [3] LILIAN BAYLIS TECHNOLOGY SCHOOL 7