COMEDK2014MathematicsPermutation and Combination
If ⁵⁶ P_ r+6 : ⁵⁴ P_ r+3 =30800: 1 , then
Options
- Ar=41
- Br=51
- Cr=31
- DNone of these
Correct answer
A. r=41
Step-by-step solution
Given, ⁵⁶ P_ r+6 :⁵⁴ P_ r+3 =30800: 1 ⁵⁶ P_ r+6 ⁵⁴ P_ r+3 = 30800 1 56 ! (51-r) ! (50-r) ! 54 ! = 30800 1 56 55 (51-r)=30800 51-r=10 r=41