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Probability

Study Material (PDF)

Study Material (PDF)

Click on each question to see answer & solution.

Question No: #21

Find the probability that the 13th day of a randomly chosen month is a Friday.

Ans: `1/84`

Question No: #22

The probability that a leap year will have 53 Fridays or 53 Saturdays is -
(a) `1/7` (b) `2/7`, (c) `3/7`, (d) `4/7`

Ans: (c) `3/7`

Question No: #23

In a non-leap year the probability of getting 53 Sundays or 53 Tuesdays or 53 Thursdays is -
(a) `1/2` (b) `2/7` (c) `3/7` (d) `4/7`

Ans: (c) `3/7`

Question No: #24

Three integers are chosen at random from the first 20 integers. The probability that their product is even is --
(a) `2/19`, (b) `17/19`, (c) `15/19`, (d) none of these

Ans: (b) `17/19`

Question No: #25

If three distinct numbers are chosen randomly from the first 100 natural numbers, then the probability that all the three numbers are divisible by both 2 and 3 is --
(a) `4/25` (b) `4/35` (c) `4/33` (d) `4/1155`

Ans: (d) `4/1155`

Question No: #26

`A` & `B` are mutually exclusive events. If `P(A) = 1/2` & `P(A \cup B) = 2/3`, then value of `P(B)` is --
(a) `1/4`, (b) `1/6`, (c) `1/3`, (d) `1/5`

Ans: (b) `1/6`

Question No: #27

Two events A & B associated with a random experiment, are such that `P(B)=0.35`, `P(A\cupB)=0.85` & `P(A\capB)=0.15`, then find `P(A)`

Ans: 0.65

Question No: #28

`A, B, C` are three events which are mutually exclusive & exhaustive. If `P(B) = 3/2\ P(A)`, `P(C) = 1/3\ P(B)`, then value of `P(C)` is --
(a) `1/6`, (b) `1/2`, (c) `1/3`, (d) `2/3`

Ans: (a) `1/6`

Question No: #29

A coin is tossed 10 time. The probability of getting 6 heads -
(a) `C_5^10 1/2^10`, (b) `C_3^10 1/2^10`, (c) `C_4^10 1/2^10`, (d) `C_8^10 1/2^10`,

Ans: (c) `C_4^10 1/2^10`

Question No: #30

Eight coins are thrown together. Find the probability that -
i) at least six heads obtained,
ii) exactly three heads obtained,

Ans: i) `37/256` ii) `7/32`

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