# Exercise 7.2(Permutations and Combinations)

### Exercise 7.2 ncert solutions maths class 11

Question 1: Evaluate

(i) 8!

(ii) 4! – 3!

Solution: (i) Given  8!

We know that 8! = 8 × 7 × 6 × 5 × 4 × 3 × 2 × 1

= 40320

(ii) Given 4!-3!

4! – 3! = (4 × 3!) – 3!

= 3! (4-1)

= 3 × 2 × 1 × 3

= 18

Question 2: Is 3! + 4! = 7!?

Solution:  LHS = 3! + 4!

3! + 4! = (3 × 2 × 1) + (4 × 3 × 2 × 1)

= 6 + 24

= 30

Taking R.H.S.

7! = 7 × 6 × 5 × 4 × 3 × 2 × 1 = 5040

Therefore LHS ≠ RHS

Therefore 3! + 4! ≠ 7!

3. Compute Solution: Given    4. If , find x.

Solution: Given,      5. Evaluate ,

When
(i) n = 6, r = 2
(ii) n = 9, r = 5

Solution: (i) Given n = 6 and r = 2

Putting the value of n and r we get     (i) Given n = 9 and r = 5

Putting the value of n and r we get     ### Chapter 7 Permutation and Combination Ncert math solution

Exercise 7.1 Permutation and Combination Ncert math solution

Exercise 7.2 Permutation and Combination Ncert math solution

Exercise 7.3 Permutation and Combination Ncert math solution

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