# Probability Quiz Set 008

### Question 1

What is the probability of getting a multiple of 3 or 5 when a dice with 20 faces numbered from 1 to 20 is tossed in the air?

A

9/20.

B

7/20.

C

1/4.

D

3/20.

Soln.
Ans: a

Total outcomes are 20. The number of favorable chances are nine: 3, 6 , 9, 12, 15, 18, 5, 10, 20. So probability is 9/20.

### Question 2

What is the probability of getting a sum of 8 from two throws of a dice?

A

4/9.

B

1/3.

C

2/3.

D

3/8.

Soln.
Ans: a

Total outcomes = 36. Favorable are 8, which are: (1, 7), (7, 1), (2, 6), (6, 2), (3, 5), (5, 3), (4, 4), (4, 4). Probability = 8/36 = 4/9.

### Question 3

Which of these cannot be a probability of an event?

A

-1.5.

B

2/3.

C

15%

D

0.7.

Soln.
Ans: a

The probability of an event is a number from 0 to +1 only. 0 means no probability and +1 means certainty.

### Question 4

A class has 7 boys and 4 girls. What is the probability of choosing 1 boy and 2 girls?

A

\${14/55}\$.

B

\$8/11\$.

C

\$15/55\$.

D

\$19/55\$.

Soln.
Ans: a

Three students have to be picked. Total number of ways = 11C3 = \${11 × 10 × 9}/{3 × 2 × 1} = \$165. Number of ways of picking 1 boy and 2 girls = 7C1 × 4C2 = 42. So probability = \$42/165\$ = \${14/55}\$.

### Question 5

From a deck of 52 cards two cards are drawn at random. What is the probability that both will be King?

A

\${1/221}\$.

B

\$4/10\$.

C

\$2/221\$.

D

\$6/221\$.

Soln.
Ans: a

Number of ways of drawing 2 cards out of 52 = 52C2 = \$(52 × 51)/2\$ = 1326. There are 4 Kings in all, so 2 can be drawn in 4C2 = \$(4 × 3)/2 = 6\$ ways. The probability is 6/1326 = \${1/221}\$. 