Question

if NC 3 is equal to 20 then find the value of n​

Answer 1

Answer:

your answer will be 12

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Answer 2

Explanation:

Correct option is

C

8

n

C

r

=

(r!)(n−r)!

n!

Given,

n

C

3

=

n

C

5

=>

(3!)(n−3)!

n!

=

5!(n−5)!

n!

=>3!×(n−3)×(n−4)×(n−5)!=5×4×3!×(n−5)!

=>(n−3)×(n−4)=5×4

From this, n−3=5

=>n=8