# (i) If 20</s

Given: 20Cr = 20Cr+6

To find: r=?

We know that:

nCr = nCn-r

20Cr+6= 20C20-(r+6)

20Cr+6= 20C20-r-6=20C14-r

20C14-r= 20Cr

14-r=r

2r=14 Ans:r=7

ii) Given: 18Cr = 18Cr+2

To find: rC5=?

We know that:

nCr = nCn-r

18Cr+2= 18C18-(r+2)

18Cr+2= 18C18-r-2=18C16-r

18C16-r= 18Cr

16-r=r

2r=16 So,

rC5= 8C5

8C5= 8C5= 8C5= 8C5= 8C5= 8C5=56

Ans: 8C5=56

Rate this question :

How useful is this solution?
We strive to provide quality solutions. Please rate us to serve you better.
Try our Mini CourseMaster Important Topics in 7 DaysLearn from IITians, NITians, Doctors & Academic Experts
Dedicated counsellor for each student
24X7 Doubt Resolution
Daily Report Card
Detailed Performance Evaluation view all courses RELATED QUESTIONS :

Prove that the prRD Sharma - Mathematics

There are 10 lampMathematics - Exemplar

If n+1RS Aggarwal - Mathematics

If nC<RS Aggarwal - Mathematics

Fill in the BlankMathematics - Exemplar

Fill in the BlankMathematics - Exemplar

The number of wayMathematics - Exemplar

Total number of wMathematics - Exemplar

The number of wayMathematics - Exemplar

The number of triMathematics - Exemplar