LESSGO A3

In a bag, there are 5 red balls and 3 blue balls. What is the probability of drawing a red ball followed by a blue ball without replacement?

• 5/24

• 2/7

• 3/8

• 15/56

A fair six-sided die is rolled. What is the probability of rolling a 3 or a 5?

• 1/4

• 1/2

• 1/3

• 1/6

If the probability of event A is 0.2 and the probability of event B is 0.3 where A and B are independent events, what is the probability of event A happening given that event B has not occurred?

• 0.1

• 0.3

• 0.2

• 0.5

In a class of 30 students, 18 are girls and 12 are boys. If a student is selected at random, what is the probability that the student is a girl?

• 0.4

• 0.6

• 0.7

• 0.5

The probability of getting a bad orange from a box is 0.2. Christina has chosen 6 oranges. Calculate the probability that

(a) only one orange is bad.

(b) all the oranges are good.

• (a) 0.3351 (b) 0.2831

• (a) 0.3932 (b) 0.2831

• (a) 0.3932 (b) 0.2621

• (a) 0.3932 (b) 0.2731

In a certain company, there are 3 out of 20 employees randomly selected, have life insurance. If there are 600 employees in the company, estimate the number of employees whose have the life insurance. Hence, calculate the variance.

• 90; 75.5

• 90; 76.5

• 90; 74.5

• 90; 73.5

A discrete random variable X has a binomial distribution, which is X∼B(n, p)   with a mean of 45 and a standard deviation of 3. Find the values of n (integer) and p.

• n = 54;  p = 0.8

• n = 56;  p = 0.6

• n = 54;  p = 0.6

• n = 56;  p = 0.8

The probability that a school bus will be late to school is 0.15. Find the probability that in 5 school’s days, the bus will be late

(a) exactly 2 days, (b) at least once.

• (a) 0.1382 ; (b) 0.5563

• (a) 0.2372 ; (b) 0.5663

• (a) 0.1352 ; (b) 0.4563

• (a) 0.2682 ; (b) 0.4593

Salmi expected to receive 4 emails in a week. Find the probability of receiving 8 emails for the next 2 weeks.

• 0.0511

• 0.0297

• 0.5470

• 0.1396

If X~Po(λ) and P(X=0) = 0.0025, find λ.

• 5

• 0

• 4

• 6