Ryan plays a game where he can score 2, 6, 10, 14 or 18 points.
The random variable XXX, representing the number of points scored, has the following probability distribution, where a a\,a and b b\,b are constants.
| xxx | 2 | 6 | 10 | 14 | 18 |
| P(X=x)P(X=x)P(X=x) | aaa | 0.15 | bbb | 0.25 | 0.30 |
The probability of scoring more than 6 is four times the probability of scoring 6 or less.
Ryan plays the game twice and adds the scores together. Each game is independent of the previous game.
Calculate the probability that the total score is 20 points.
57 exam-style questions on Edexcel AS Level Maths Statistical Distributions, covering 6.1 Probability Distributions, 6.2 The Binomial Distribution, and 6.3 Cumulative Probabilities. Each one has a worked solution and a mark scheme showing where the marks go.