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Praetorian
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anandnk
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Geethu
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Another vote for 25*24*23*21;

Explanation:
First select consonant for 4th place, one can do that in 21 ways. now not to repeat that consonant again select 1st, 2nd and 3rd place in 25, 24 and 23 ways respectively.

Cheers :) , Dharmin
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Praetorian
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praetorian123
Rules

1. Time yourself
2. Work your solution on a seperate sheet of paper
3. write your solution here , and your time please

I say it again, we request your timings for different problems. this will help us in our project. you can just say >2 min or <2 min...something like that.

How many four letter distinct initials can be formed using the alphabets of English language such that the last of the four words is always a consonant?

[ Consonant => all aphabets except the vowels A,E,I,O and U ]

1) (26^3)*(21)
2) 26*25*24*21
3) 25*24*23*21
4) 25^3*21


Edit: thanks kpadma, the correction has been done.

1) 26^3 * 21 is the answer. Good Discussion guys.
The question asks you to find out the number of distinct initials and not initials where the letters are distinct.
anandnk, is that clear now?
First letter can be arranged in 26 ways
Second letter can be arranged in 26 ways
Third letter can be arrranged in 26 ways

last one...NO vowels...so 26- 5 =21 ways

26^3 * 21 ways

Answer A

thanks all
praetorian
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kpadma
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praetorian123
4) 25^3 * 21 is the answer. Good Discussion guys.

last one...NO vowels...so 26- 5 =21 ways

26^3 * 21 ways

Answer A

thanks all
praetorian


Dear Praetorian,

Is it 25^3 * 21 or 26^3 * 21?
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Makky07
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Geethu and Dharmin,

Distinct initials = 26^3 * 21
Even if the first three letter are the same, the last consonant is sufficient to make all the initials distinct. BBBC is not the same as CBBB because we're talking initials.
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Geethu
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Thank you ndidi204.

anandnk, which probability book are you using. I haven't given any specific study to this topic separately. But you seem to give exact answers.
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Makky07
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Hey Geethu,

I recommend "Probability Without Tears" by Derek Rowntree. Great book. Completely explains probability/combinations/permuations in a very clear and straightforward manner. You can borrow it from your local library if you don't want to buy it.

It also gives several good examples.
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Hi Geethu,

I didnt use any probability book. I just learnt it in this club by carefully analyzing every post. Very few times I visited
https://mathworld.wolfram.com/

Probability is one subject you will either hate or love.

Anand.



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