1.

How many words can be formed by rearranging the alphabets of word 'REHABILITATION'? (must not necessarily have meaning)1. \(\rm 14!\over2!\times2!\)2. \(\rm 14!\over2!\times3!\)3. \(\rm 14!\over2!\times2!\times3!\)4. \(\rm 14!\over4!\times3!\)

Answer» Correct Answer - Option 3 : \(\rm 14!\over2!\times2!\times3!\)

Concept:

  • The ways of arranging n different things = n!
  • The ways of arranging n things, having r same things and rest all are different = \(\rm n!\over r!\)
  • The no. of ways of arranging the n arranged thing and m arranged things together = n! × m!
  • The number of ways for selecting r from a group of n (n > r) = nCr 


Calculation:

R E H A1 B I1 L I2 T1 A2 T2 I3 O N

Total of letters = 14

There are 2 A's, 3 I's, 2 T's, 

∴ The number of words formed = \(\rm 14!\over2!\times2!\times3!\)



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