Permutation and Combination



Practice Questions - Permutation and Combination

Q1) There are 5 seats available in a car. In how many ways can they five people be seated if only two can drive.
1)
72
2) 24
3) 48
4) 64


Driver can be chosen in 2 ways.
Required ways = 2×4×3×2×1 = 48
Hence, option 3.



Q2) A multiple choice exam contains 5 questions, each having 4 possible answers. How many different ways are there to complete the exam?
1)
45
2) 54
3) 55
4) 20


Required ways = 4×4×4×4×4 = 45
Hence, option 1.


Formation of words with Given Letters:


Number of permutations of 'n' objects out of which p are alike and are of one type, q are alike and are of second type and r are alike and are of third type



Download: Seating Arrangement around Geometrical Figures

Example:How many different words with or without meaning can be formed by using all the letters of the word ‘DIRECTOR’?

Solution:
Total number of letters = 8. Here, R occurs 2 times.
Total number of arrangements =

Q3 How many different words with or without meaning can be formed by using all the letters of the word ‘MATHEMATICS’.
1)

2)
3)
4)


Total words that can be formed is
Hence, option 1.


Q4) If you have 7 books, in how many ways can you select five books and arrange them on a shelf?
1)
120
2) 5040
3) 21
4) 2520


Required ways = P(7,5) = 2520
Hence, option 4.


Q5) An unbiased coin is tossed 5 times. How many different outcomes have exactly 3 tails?
1)
3
2) 10
3) 6
4) 60


Having exact 3 tails = C(5,3) = 10
Hence, option 2.



Q6) An unbiased coin is tossed 5 times. How many different outcomes have atmost 2 heads?
1)
15
2) 64
3) 10
4) 16


Number of different outcomes have atmost 2 heads = 5C0 + 5C1 + 5C2 = 16
Hence, option 4.



Q7) A bag contains 6 red and 4 black balls. In how many ways can we withdraw 5 balls out of which 3 are red?
1)
120
2) 20
3) 252
4) None of these


Required ways = 6C3.4C2 = 120
Hence, option 1.



Q8) 8 friends have to be seated in a row for a group photo. In how many ways can they be seated in a row so that a particular person is always to the left of A.
1)
20160
2) 5040
3) 10080
4) 2520


Required ways = = 20160
Hence, option 1.


Q9) Six friends go to watch a movie. In how many ways can they be seated in a row of six seats so that three of them are always together.
1)
120
2) 720
3) 36
4) 144


Friends who are always together can be treated as a group so 4 things can be arranging in a linear manner in ways.
Internal arrangement of these 3 friends =
Total number of ways = = 144
Hence, option 4.


Download: Permutation and Combination Practice Questions


Q10) A bag contains 8 apples out of which 3 apples are rotten. In how many ways can you select a sample of 4 apples out of which at least 1 apple and at most 2 apples are rotten.
1)
65
2) 60
3) 56
4) 70


Required ways = C(3,1).C(5,3) + C(3,2).C(5,2) = 60
Hence, option 2.