NCERT Solutions For Class 11 Math Chapter – 7 Exercise – 7.2
Q1. Evaluate
- 8!
- 4! – 3!
Solution:-
- 8! = 1 x 2 x 3 x 4 5 x 6 x 7 x 8 = 40320
- 4! = 1 x 2 x 3 x 4 = 24
3! = 1 x 2 x 3 = 6
4! – 3! = 24 – 6 = 18
Q2. Is 4! + 3! = 7! ?
Solution:-
3! = 1 x 2 x 3 = 6
4! = 1 x 2 x 3 x 4 = 24
Therefore,
3! + 4! = 6 + 24 = 30
7! = 1 x 2 x 3 x 4 x 5 x 6 x7 = 5040
Hence 3! + 4! ≠ 7!
Q3. Compute 8!/6! x 2!
Solution:-
8!/6! x 2! = 8×7/2 = 28
Q4. If 1/6! + 1/7! = x/8! find x.
Solution:-
1/6! + 1/7! = x/8!
1/6! + 1/7! = x/8 x 7 x 6!
1/6! (1+1/7) = x/8 x 7 x 6!
X = 64
Q5. Evaluate n!/(n-r)! when
- n = 6 r = 2
- N = 9 , r = 5
Solution:-
- N!/(n-r)! = 6!/(6-2)!
= 6!/5!
= 6 x 5 x 4!/4!
= 30
- When n = 9 r = 5!
N!/(n-r)! = 9!/(9-5)!
= 9!/4!
= 9 x 8 x 7 x 6 x 5 x 4!/4!
= 15120