Eli has four fair 4-sided dice with sides labelled 1, 2, 3, 4. He throws all four dice at the same time. The random variable X denotes the number of 2s obtained.
(b) Complete the following probability distribution table for X.
| x | 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|
| P(X = x) | \(\frac{81}{256}\) | \(\frac{3}{64}\) | \(\frac{1}{256}\) |
Eli throws the four dice at the same time on 96 occasions.
(d) Use an approximation to find the probability that he obtains at least two 2s on fewer than 20 of these occasions.
On a certain road 20% of the vehicles are trucks, 16% are buses and the remainder are cars.
A random sample of 125 vehicles is now taken. Using a suitable approximation, find the probability that more than 73 are cars.
On a production line making toys, the probability of any toy being faulty is 0.08. A random sample of 200 toys is checked. Use a suitable approximation to find the probability that there are at least 15 faulty toys.
A die is biased so that the probability of throwing a 5 is 0.75 and the probabilities of throwing a 1, 2, 3, 4 or 6 are all equal.
On any occasion when a particular gymnast performs a certain routine, the probability that she will perform it correctly is 0.65, independently of all other occasions.
On one day she performs the routine 50 times. Use a suitable approximation to estimate the probability that she will perform the routine correctly on fewer than 29 occasions.