Question

if nc10 = nc4 then 25c25 is​

Answer 1

Answer:

n

C

10

=

n

C

15

. ....(1)

We know that

n

C

r

=

n

C

n−r

,

n

C

10

=

n

C

n−10

=

n

C

15

, ....by (1)

∴ n - 10 =15 or n = 25

or If

n

C

x

=

n

C

y

then x + y = n.

Hence from (1), we get 10 + 15 = 25= n

∴

27

C

n

=

27

C

25

=

27

C

27−25

=

27

C

2

=

1×2

27×26

=27×13=351