1.

Three letters are randomly selected from the 26 capital letters of the English alphabet. What is the probability that letters A will not be included in the choice ?(a) \(\frac{1}{12}\)(b) \(\frac{23}{26}\)(c) \(\frac{12}{13}\)(d) \(\frac{25}{26}\)

Answer»

(b) \(\frac{23}{26}\)

Total number of ways in which 3 letters can be selected from 26 letters 

= 26C3

If A is not to be included in the choice, there are 25 letters left, so number of ways in which 3 letters can be selected without including A 

= 25C3

∴ Required probability = \(\frac{^{25}C_3}{^{26}C_3}\) = \(\frac{25\times24\times23}{26\times25\times24}\) = \(\frac{23}{26}\).



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