Question

permutations and combination

IF 18Cr = 18Cr+2 ,the value of rC5 is..??

a) 55
b) 50
c) 56
d) none ​

Answer 1

Question:-

IF 18Cʀ = 18Cʀ+2 ,ᴛʜᴇ ᴠᴀʟᴜᴇ ᴏғ ʀC5 ɪs..??

ᴀ) 55

ʙ) 50

ᴄ) 56

ᴅ) ɴᴏɴᴇ

Solution:-

Answer:-

• 56 (ᴄ ᴏᴘᴛɪᴏɴ) ɪs Cᴏʀʀᴇᴄᴛ.

Explaination:-

$¹⁸cr = ¹⁸cr + 2 \\ so \: \: r = r + 2 \: or \: 18 - r = \: r \: + 2 \\ 16 = 2r \\ r = 8 \\ so \: ⁸c5 = \frac{8}{53} \\ = \frac{6 \times 7 \times 8}{6 } \\ 56$

Hence:-

Hᴇɴᴄᴇ, ᴛʜᴇ ᴀɴsᴡᴇʀ ɪs 56.

Answer 2

Question:-

permutations and combination

IF 18Cr = 18Cr+2 ,THE VALUE OF rC5 is??

a) 55

b) 50

c) 56

d) none

Solution:-

Given:-

18Cr = 18Cr+2

Find out :-

The value of rC5.

Step-by-step:-

18 = r+r+2

18 - 2=2r

r = 8

8C5

[ 8×7×6×5×4 ]\120

= 56

Final solution:-

56..........

hence, C option is correct