NCERT Class 11-Math's: Chapter –7 Permutations and Combinations Part 5

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7.3 EXERCISE

Short Answer Type

Question 1:

Eight chairs are numbered 1 to 8. Two women and 3 men wish to occupy one chair each. First the women choose the chairs from amongst the chairs 1 to 4 and then men select from the remaining chairs. Find the total number of possible arrangements.

[Hint: 2 women occupy the chair, from 1 to 4 in ways and men occupy the remaining chairs in ways.]

Answer:

Question 2:

If the letters of the word RACHIT are arranged in all possible ways as listed in dictionary. Then what is the rank of the word RACHIT?

[Hint: In each case number of words beginning with A, C, H, I is ]

Answer:

Question 3:

A candidate is required to answer 7 questions out of 12 questions, which are divided into two groups, each containing 6 questions. He is not permitted to attempt more than 5 questions from either group. Find the number of different ways of doing questions.

Answer:

Question 4:

Out of 18 points in a plane, no three are in the same line except five points which are collinear. Find the number of lines that can be formed joining the point.

[Hint: Number of straight lines =]

Answer:

Question 5:

We wish to select 6 persons from 8, but if the person A is chosen, then B must be chosen. In how many ways can selections be made?

Answer:

Question 6:

How many committee of five persons with a chairperson can be selected from 12 persons.

[Hint: Chairman can be selected in 12 ways and remaining in.]

Answer:

Question 7:

How many automobile license plates can be made if each plate contains two different letters followed by three different digits?

Answer:

Question 8:

A bag contains 5 black and 6 red balls. Determine the number of ways in which 2 black and 3 red balls can be selected from the lot.

Answer:

Question 9:

Find the number of permutations of distinct things taken r together, in which 3 particular things must occur together.

Answer:

Question 10:

Find the number of different words that can be formed from the letters of the word ‘TRIANGLE’ so that no vowels are together

Answer:

Question 11:

Find the number of positive integers greater than and less than which are divisible by 5, provided that no digit is to be repeated.

Answer:

Question 12:

There are persons named . Out of persons, 5 persons are to be arranged in a line such that in each arrangement must occur whereas and do not occur. Find the number of such possible arrangements.

[Hint: Required number of arrangement ]

Answer:

Formula:-

Given:- There are person named .

Number of ways of arrangement

Number of ways arrangement of other

Therefore, required number of arrangement