YEAR 9RevisionUNIT 21: Probability
- 140 students each study one language as shown in the table below.
French / Spanish / German / Total
Female / 10
Male / 40 / 72
Total / 40 / 30 / 140
- Complete the table.
- If one student is picked at random, what is the probability that they study Spanish?
- A biased die has a probability of 0.45 of landing on a 1. If you roll the die 900 times, work out an estimate for the number of 1’s you will score.
- A bag contains 2 red beads, 4 black beads and 3 green beads.
- Complete the possibility space diagram to show all the possible outcomes of picking a bead at random and replacing it, then doing the same again.
R / R / B / B / B / B / G / G / G
R / R, R / R, R / R,B / R, G
R / R, R / R, R
B / B, R / B, B
B / B, R
B / B, R
B / B, R / B, B
G / G, R
G / G, R
G / G, R / G, R / G, B
- How many possible outcomes of the experiment are there?
- Use your table to calculate the probability that both beads are the different colours.
- A young baby can be on happy, crying or asleep. The probability that the baby is happy is 0.12, the probability that it is asleep is 0.58. What is the probability that it is crying?
- Melissa says that the probability that she is naughtyfor mummy tonight is 0. She is wrong. Explain why.
- Dan and James take a test. The probability that Dan passes is 0.85 and the probability that James passes is 0.7.
- Complete a tree diagram.
- Calculate the probability that only one of them passes the test.
- Fredexperiments. He tosses a coin 50 times. He gets tails35 times. Is the coin fair? Explain your answer.
- The probability that Callum is late for school tomorrow is 0.2 and the probability that Martin is late for school is 0.4. The two events are independent.
- What is the probability that both boys are late?
- What is the probability that neither boy is late? (3 marks)