NCERT Class 11-Math's: Exemplar Chapter –16 Probability Part 5

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Objective Type Questions

Choose the Correct Answer from Given Four Options in Each of the Examples 9 to 15 (M.C.Q.)

Question 9:

In a leap year the probability of having Sundays or Mondays is

(A)

(B)

(C)

(D)

Answer:

(B) Is the correct answer.

Since a leap year has 366 days and hence weeks and days. The days can be .

Therefore,

Question 10:

Three digit numbers are formed using the digits . A number is chosen at random out of these numbers. What is the probability that this number has the same digits?

(A)

(B)

(C)

(D)

Answer:

(D) Is the correct answer. Since a digit number cannot start with digit , the hundredth place can have any of the 4 digits. Now, the tens and units place can have all the digits. Therefore, the total possible 3-digit numbers are , i.e., .

The total possible 3 digit numbers having all digits same

Hence,

Question 11:

Three squares of chess board are selected at random. The probability of getting 2 squares of one colour and other of a different colour is

(A)

(B)

(C)

(D)

Answer:

(A) is the correct answer. In a chess board, there are 64 squares of which 32 are white and 32 are black. Since 2 of one colour and 1 of other can be 2W, 1B, or 1W, 2B, the number of ways is and also, the number of ways of choosing any 3 boxes is .

Hence, the required probability

Question 12:

If A and B are any two events having then the probability of is

(A)

(B)

(C)

(D)

Answer:

We have

Question 13:

Three of the six vertices of a regular hexagon are chosen at random. What is the probability that the triangle with these vertices is equilateral?

Answer:

(D) is the correct answer.

ABCDEF is a regular hexagon. Total number of triangles. (Since no three points are collinear). Of these only ; are equilateral triangles.

Therefore, required probability