permutation and combination aptitude tricks - Wikitechy https://www.wikitechy.com/interview-questions/tag/permutation-and-combination-aptitude-tricks/ Interview Questions Mon, 06 Sep 2021 09:30:16 +0000 en-US hourly 1 https://wordpress.org/?v=6.9.4 https://www.wikitechy.com/interview-questions/wp-content/uploads/2025/10/cropped-wikitechy-icon-32x32.png permutation and combination aptitude tricks - Wikitechy https://www.wikitechy.com/interview-questions/tag/permutation-and-combination-aptitude-tricks/ 32 32 If 56Pr+ 6 : 54Pr + 3 = 30800 : 1 then the value of r is ? https://www.wikitechy.com/interview-questions/permutation-and-combination/if-56pr-6-54pr-3-30800-1-then-the-value-of-r-is/ https://www.wikitechy.com/interview-questions/permutation-and-combination/if-56pr-6-54pr-3-30800-1-then-the-value-of-r-is/#respond Tue, 17 Aug 2021 20:57:58 +0000 https://www.wikitechy.com/interview-questions/?p=1952

If 56Pr + 6 : 54Pr + 3 = 30800 : 1 then the value of r is ?

A. 40

B. 41

C. 42

D. None of these

Answer : B. 41

Explanation :

56Pr + 6 = 56! / [56 – (r + 6) ]! = 56! / (50 – r)!
54Pr + 3 = 54! / [54 – (r + 3) ]! = 54! / (51 – r)!
56Pr + 6 / 54Pr + 3 = [ ( 56! / (50 – r)! ) x ( (51 – r)! / 54!) ] ( 56 x 55 x 54! / (50 – r)! ) x ( (51-r).(50-r)! ) / 54 !
= 56 x 55 x (51-r)

56Pr + 6 / 54Pr + 3 = 30800 / 1
=> 56 x 55 x (51-r) = 30800
=> (51-r) = 10
=> r = 41

]]> https://www.wikitechy.com/interview-questions/permutation-and-combination/if-56pr-6-54pr-3-30800-1-then-the-value-of-r-is/feed/ 0 Find the value of 5P2 ? https://www.wikitechy.com/interview-questions/permutation-and-combination/find-the-value-of-5p2/ https://www.wikitechy.com/interview-questions/permutation-and-combination/find-the-value-of-5p2/#respond Tue, 17 Aug 2021 20:48:40 +0000 https://www.wikitechy.com/interview-questions/?p=1947

Find the value of 5P2 ?

A . 15

B . 18

C . 20

D . 122

Answer : C . 20

Explanation :

5P2 = 5 ! / (5 – 2) ! = 5 x 4 = 20

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