7 STEM The table shows the percentage of computer failures caused by each component. Computer part Percentage of failures Motherboard 8 RAM 24 CPU 3 Hard disk 22 PSU 34 Disk drive 6 Other 3 a A computer breaks down. What is the probability that i it has a faulty motherboard or hard disk ii it does not have a faulty PSU or CPU? b 80 computers break down. How many do you expect to i have a faulty hard disk ii have a faulty RAM, disk drive or CPU? Discussion A shop finds that on average 2 out of 5 computers of a certain brand have faulty RAM. Is this brand worse than average? 8 Annabel rolls an ordinary 4-sided dice and Ben spins the fair spinner. The player with the higher number wins a point. Neither player wins if the numbers are the same. Annabel 1 6 a List the possible outcomes. b Is the game fair? Explain your answer. Ben 3 1 1 4 Q8a hint c Annabel and Ben win 60 points between them. How many points would you expect each player to have won? Draw a table. 9 Reasoning Some students built this game to raise money for charity. A ball falls at random into one of the holes. Red wins a prize of 50p, blue wins 20p, yellow wins nothing. a Copy the table and complete the first three columns. Colour Probability Prize Expected number of wins in 200 games Expected prizes in 200 games b In 200 games i how many times would you expect the ball to fall into each colour? Fill in the fourth column. ii how much money would be won on each colour? Fill in the last column. iii how much are the expected prizes in total? c How much should the students charge to play the game to make a profit? Explain your answer. Unit 8 Probability 196