NCERT Solutions Class 11th Maths Chapter – 7 Permutations and Combinations Exercise 7.2
| Textbook | NCERT |
| class | Class – 11th |
| Subject | Mathematics |
| Chapter | Chapter – 7 |
| Chapter Name | Permutations and Combinations |
| grade | Class 11th Maths solution |
| Medium | English |
| Source | last doubt |
NCERT Solutions Class 11th Maths Chapter – 7 Permutations and Combinations Exercise 7.2
?Chapter – 7?
✍Permutations and Combinations✍
?Exercise 7.2?
1. Evaluate
(i) 8!
(ii) 4! – 3!
Solution:
(i) Consider 8!
We know that 8! = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1
= 40320
(ii) Consider 4!-3!
4!-3! = (4 × 3!) – 3!
Above equation can be written as
= 3! (4-1)
= 3 × 2 × 1 × 3
= 18
2. Is 3! + 4! = 7!?
Solution:
Consider LHS 3! + 4!
Computing left hand side, we get
3! + 4! = (3 × 2 × 1) + (4 × 3 × 2 × 1)
= 6 + 24
= 30
Again consider RHS and computing we get
7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040
Therefore LHS ≠ RHS
Therefore 3! + 4! ≠ 7!
3. Compute
Solution:
4. If
find x.
Solution:
5. Evaluate
When
(i) n = 6, r = 2
(ii) n = 9, r = 5
Solution:
