Question

nc2 = 45 find n (it's from combinations)

Answer 1

ur answer is n=10
hope
... it help u

Answer 2

The value of n = 10

Given :

$\displaystyle \sf{ {}^{n}C_2 = 45 }$

To find :

Find the value of n

Solution :

Step 1 of 2 :

Write down the given equation

Here the given equation is

$\displaystyle \sf{ {}^{n}C_2 = 45 }$

Step 2 of 2 :

Find the value of n

$\displaystyle \sf{ {}^{n}C_2 = 45 }$

$\displaystyle \sf{ \implies {}^{n}C_2 = 5 \times 9}$

$\displaystyle \sf{ \implies {}^{n}C_2 = \frac{10 \times 9}{2} }$

$\displaystyle \sf{ \implies {}^{n}C_2 = \frac{10 \times 9 \times 8!}{8! \times 2!} }$

$\displaystyle \sf{ \implies {}^{n}C_2 = \frac{10 !}{8! \times 2!} }$

$\displaystyle \sf{ \implies {}^{n}C_2 = \frac{10 !}{2! \times 8!} }$

$\displaystyle \sf{ \implies {}^{n}C_2 = \frac{10 !}{2! \times (10 - 2)!} }$

$\displaystyle \sf{ \implies {}^{n}C_2 = {}^{10}C_2 }$

$\displaystyle \sf{ \implies n = 10 }$

Hence the required value of n = 10

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