Class 11 Maths NCERT Solutions for Chapter 7 Permutations and Combinations Exercise 7.2
![Class 11 Maths NCERT Solutions for Chapter 7 Permutations and Combinations Exercise 7.2 Class 11 Maths NCERT Solutions for Chapter 7 Permutations and Combinations Exercise 7.2](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVA8voTcLEloF7jfDcLDvjO3fpNr3ApPMLKYgM_D1It_g0Uyt0wf1oT4xwFbqkRW3K0krTrn1UuFyVV8wTIrXl91i-FRGwrMm7D0AeKjN8eJ4ieTeWQgQngy41mvuoC2mkbemhbJ6KuW9aDZuKCXxl72znYjQdkFxTEJuFrXcNKhf6QrHGVcaXIYS3/w657-h310-rw/ncert-solutions-for-class11-maths-permutations-and-combinations-exercise-7-2.jpg)
Permutations and Combinations Exercise 7.2 Solutions
1. Evaluate
(i) 8!
(ii) 4! – 3!
Solution
(i) 8! = 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8 = 40320
(ii) 4! = 1 × 2 × 3 × 4 = 24
3! = 1 × 2 × 3 = 6
∴ 4! – 3! = 24 – 6 = 18
2. Is 3! + 4! = 7!?
Solution
3! = 1 × 2 × 3 = 6
4! = 1 × 2 × 3 × 4 = 24
∴3! + 4! = 6 + 24 = 30
7! = 1 × 2 × 3 × 4 × 5 × 6 × 7 = 5040
∴ 3! + 4! ≠ 7!
3.Compute 8!/(6! × 2!)
Solution
4. If 1/6! + 1/7! = x/8! , find x.
Solution
∴ x = 64
5 Evaluate n!/(n - r)! , when
(i) n = 6, r = 2
(ii) n = 9, r = 5
(i) n = 6, r = 2
(ii) n = 9, r = 5
Solution
(i) When n = 6, r = 2
![](https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiG4VR3VU88N79r5DDIP5BFXv9l0Jbq3yvFaP2kmV2tCOLBaDq0JgYRzmOpkTlWbl4sUKWkv09n3vCvcUNn3ZQaWfmunEBaFNAfrW35_phciUzifow_CbfJ6JP7YaNTRusyV5XQrjhLvjuzTtx6YJAkxgGhmYqkAmI2HzZRAoyGVzFWkMVO87tD0RQc/w285-h48-rw/NCERT%20Solution%20For%20Class%2011%20Math%20Chapter%207%20Permutations%20and%20Combinations%20Exercise%207.2%20img%203.JPG)
(ii) When n = 9, r = 5,
= 9 × 8 ×7 × 6 × 5 = 15120