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Probability

Important Instructions
11.

A bag contains 6 black, 7 red and 2 white balls. A ball is drawn from the bag at random. Find the probability that the ball drawn is black or white.

Answer: A

Total number of balls = 15

Number of balls that are either black or white = 8

Hence the number of favourable outcomes of ball drawn being black or white is 8.

We know that, Probability of an event E, P (E) =number of favourable outcomes/total number of outcomes

So, the required probability is 8/15.

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12.

There are 5 green, 6 black and 7 white balls in a bag. A ball is drawn at random from the bag. Find the probability that it is not white.

Answer: D

Given,

Number of green balls = 5

Number of black balls = 6

Number of white balls = 7

Total number of outcomes = 5 + 6 + 7 = 18

There are 18 balls out of which 11 are not white.

⇒ Number of favourable outcomes = 11

Probability of an event, P (E) = =Number of favourable outcomes / Total number of outcomes

⇒ P (ball drawn is not white) = 11/18

Therefore, probability that the ball drawn is not white is 11/18.

Alternate Method:

P (ball drawn is white) = 7/18

We know that,

P (ball drawn is white) + P (ball drawn is not white) = 1

Because the sum of the probability of an event and its complementary event is always 1.

⇒ P (ball drawn is not white) = 1 – P (ball drawn is white) = 1−7/18 = 11/18

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13.

From a well-shuffled pack of 52 cards, a card is drawn at random, find the probability that it is a spade.

Answer: B

There are 13 spades in a deck of 52. Hence, the probability of drawing a spade is 13/52 = ¼

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14.

What will be the possibility of drawing a jack or a spade from a well shuffled standard deck of 52 playing cards?

Answer: A

No answer description available for this question.

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15.

Two dice are thrown at the same time. Find the probability of getting different values on both.

Answer: A

Let E be the event of getting different values on both the dice. The complementary event is getting the same value on both, for which there are 6 favorable outcomes: (1,1), (2,2), (3,3), (4,4), (5,5) and (6,6). Thus, P (not E) = 1/6

Thus, P (E) = 1 – P (not E) = 1 – (1/6) = 5/6

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16.

The sum of the probability of an event and non event is :

Answer: B

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17.

Suresh keeps all his socks in a single drawer. He has 24 pairs of white socks and 18 pairs of grey socks. Suresh picks 3 socks randomly. Find the possibility of Suresh choosing a matching pair.

Answer: D

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18.

If two dice are thrown together, the probability of getting an even number on one die and an odd number on the other is -.

Answer: B

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19.

A pot has 2 white, 6 black, 4 grey and 8 green balls. If one ball is picked randomly from the pot, what is the probability of it being black or green?

Answer: B

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20.

Two cards are drawn together from a pack of 52 cards. The probability that one is a spade and one is a heart, is:

Answer: D

No answer description available for this question.

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