Question

if nc2=15 then find value of N?​

Answer 1

compare with 6C2

answer will be n=6

as (6!) / (4!2!) = 720 / 2*24 = 15

Answer 2

$\displaystyle \sf{ If \: \: {}^{n} C_2 = 15 \: \: then \: \: n = 6}$

Given :

$\displaystyle \sf{ {}^{n} C_2 = 15 }$

To find :

The value of n

Solution :

Step 1 of 2 :

Write down the given equation

The given equation is

$\displaystyle \sf{ {}^{n} C_2 = 15 }$

Step 2 of 2 :

Find the value of n

$\displaystyle \sf{ {}^{n} C_2 = 15 }$

$\displaystyle \sf{ \implies {}^{n} C_2 = 5 \times 3}$

$\displaystyle \sf{ \implies {}^{n} C_2 = \frac{6 \times 5}{2} }$

$\displaystyle \sf{ \implies {}^{n} C_2 = \frac{6 \times 5 \times 4!}{4! \times 2} }$

$\displaystyle \sf{ \implies {}^{n} C_2 = \frac{6 !}{4! \times 2! } }$

$\displaystyle \sf{ \implies {}^{n} C_2 = {}^{6} C_2 }$

$\displaystyle \sf{ \implies n = 6}$

Hence the required value of n = 6

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