Rules 1. Time yourself 2. Work your solution on a seperate

Question

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 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

anandnk · Answer

less than 10 seconds

26^3 * 21

I dont understand what you mean by distinct initials.

is AAAA a distcint initial or not ?

Geethu · Answer

3) 25*24*23*21 
I assumed distinct initial means ABCD without repeating them in the same set.

I took 1 min.

Dharmin · Answer

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

Praetorian · Answer

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

kpadma · Answer

Dear Praetorian,

Is it 25^3 * 21 or 26^3 * 21?

Makky07 · Answer

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.

Geethu · Answer

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.

Makky07 · Answer

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.

anandnk · Answer

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.

Rules 1. Time yourself 2. Work your solution on a seperate

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