Class 11 Mathematics Permutations & Combinations: NCERT Solutions for Question 6
Given 5 flags of different colours, how many different signals can be generated if each signal requires the use of 2 flags, one below the other?
Each signal requires the use of 2 flags.
There will be as many flags as there are ways of filling in 2 vacant places
in succession by the given 5 flags of different colours.
The upper vacant place can be filled in 5 different ways by any one of the 5 flags following which, the lower vacant place can be filled in 4 different ways by any one of the remaining 4 different flags.
Thus, by multiplication principle, the number of different signals that can be generated is 5 × 4 = 20
Popular Questions of Class 11 Mathematics
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Find the sum of integers from 1 to 100 that are divisible by 2 or 5.
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If the sum of three numbers in A.P., is 24 and their product is 440, find the numbers.
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A wheel makes 360 revolutions in one minute. Through how many radians does it turn in one second?
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The sum of the first four terms of an A.P. is 56. The sum of the last four terms is 112. If its first term is 11, then find the number of terms.
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How many terms of G.P. 3, 32, 33, … are needed to give the sum 120?
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Find the sum of all numbers between 200 and 400 which are divisible by 7.
- Q:- Write the following sets in roster form:
(i) A = {x: x is an integer and - 3 < x < 7}.
(ii) B = {x: x is a natural number less than 6}.
(iii) C = {x: x is a two-digit natural number such that the sum of its digits is 8}
(iv) D = {x: x is a prime number which is divisor of 60}.
(v) E = The set of all letters in the word TRIGONOMETRY.
(vi) F = The set of all letters in the word BETTER. - Q:-
Insert five numbers between 8 and 26 such that the resulting sequence is an A.P.
- Q:-
Find the sum of all two digit numbers which when divided by 4, yields 1 as remainder.
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Find the derivative of 99x at x = l00.
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(i) (3, 6, 9, 12)
(ii) {2, 4, 8, 16, 32}
(iii) {5, 25, 125, 625}
(iv) {2, 4, 6 upto infinity}
(v) {1, 4, 9, upto 100} - Q:-
Find the sum of all numbers between 200 and 400 which are divisible by 7.
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