Question

6. A number is selected at random from the numbers 1 to 20 inclusive a) What is the probability that the number is even (E)? b) What is the probability that the mumber is divisible by 5? 7. A letter is chosen at random from the word "TEAM". What is the probability that it is a vowel? 8. Fifteen persons reporting to a Red Cross center one day are typed for blood. and the following counts are found: 0 = 3. A = 5, B = 6, AB = 1. If one person is randomly selected, what is the probability that this person's blood group is a) AB? b) Either A or B? c) O? d) Not O?

Answer 1

Explanation:

a probability is always the ratio

desired cases / totally possible cases

6a)

in the interval [1 .. 20] are 20 numbers, and half of them (20/2 = 10) are even.

the probabilty that the random number is even is

10/20 = 1/2 = 0.5

6b)

in the interval only the numbers 5, 10, 15, 20 are divisible by 5. that is 4 cases.

the probabilty is

4/20 = 1/5 = 0.2

7.

TEAM has 4 letters. 2 of them are vowels (A and E).

the probability to get a vowel is

2/4 = 1/2 = 0.5

8.

15 totally possible cases.

a)

1 desired case for AB.

the probabilty for it is

1/15 = 0.066666666...

b)

either A or B means 5+6 = 11 desired cases.

the probability is

11/15 = 0.733333333...

c)

3 desired cases for O.

the probability is

3/15 = 1/5 = 0.2

d)

5+6+1 = 12 people are not O.

the probabilty for that is

12/15 = 4/5 = 0.8