English
Hindi
6.Permutation and Combination
easy

જો $^nC_{15}= ^nC_8$ હોય, તા $^nC_{21}$ નું મૂલ્ય કેટલું થાય ?

A

$220$

B

$253$

C

$310$

D

આપેલ પૈકી એકપણ નહિ

Solution

$^nC_{15} = ^nC_8 ⇒ n = (15 + 8) = 23$  $ [ ^nC_x = ^nC_y ⇒ x + y = n]$

$^nC_{21} = ^{23}C_{21} = ^{23}C_{23-21}  $

$^nC_r = ^nC_n – r= ^{23}C_2= 253$

Standard 11
Mathematics

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