Test Index

NCERT Class XI Mathematics - Permutations and Combinations - Solutions

© examsnet.com
Question : 22
Total: 41
If
n
‌
C8 =
n
‌
C2 , find
n
‌
C2
Solution:  
We have ,
n
‌
C8 =
n
‌
C2
⇒
n
‌
C8 =
n
‌
Cn−2 [Since
n
‌
Cr =
n
‌
Cn−r]
⇒ 8 = n - 2 [Since
n
‌
Ca =
n
‌
Cb ⇒ a = b] ⇒ n = 10
∴
n
‌
C2 =
10
‌
C2 =
10!
2!8!
 =
10×9
2
 = 45
© examsnet.com
Go to Question:
Prev Question
Next Question