IMMEDIATE

How many ways can you arrange the word I M M E D I A T E IMMEDIATE where T T would be in first and A A in last?

IMMEDIATE \huge \text{IMMEDIATE}


  • For example: T I M M E D I E A TIMMEDIEA and T E I M M E D I A TEIMMEDIA where T T in first and A A in last.


The answer is 630.

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2 solutions

Kb E
Nov 12, 2017

We are looking for arrangements of the form T _ _ _ _ _ _ _ A . If the letters in between were all distinct, we would have 7 ! = 5040 7! = 5040 possibilities. However, the letters I , M , and E I, M, \text{and } E occur twice. For each of these, the possibilities are counted twice (for example the arrangement T _ E _ E _ _ _ A ) occurs twice in 5040). Therefore, we need to divide the total possibilities by 2 for each of these letters and the answer is 7 ! 2 3 = 5040 8 = 630 \frac{7!}{2^3} = \frac{5040}{8} = 630 .

Md Mehedi Hasan
Nov 12, 2017

For T T in first and A A in last, we have to give up them from arrangement. Because they are state and they have a fixed position.

Then we have 2 I 2I , 2 E 2E , 2 M 2M and 1 D 1D for arrange

So we get the total arranges are = 7 ! 2 ! × 2 ! × 2 ! = 630 =\frac{7!}{2!\times2!\times2!}=\boxed{630}

I didn't understand.

Munem Shahriar - 3 years, 7 months ago

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Aren't you clear? If didn't you can tell me.

Md Mehedi Hasan - 3 years, 7 months ago

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Well, perhaps I am wrong, but I would like to know why.

Munem Shahriar - 3 years, 7 months ago

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@Munem Shahriar you would right if I asked how many arrange we get without any condition. But I asked, there A and T have a fixed position. So we have to make arrange without them. You should remember that, who are fixed in a position, they can not be arranged always we have to give up them from calculation.

Let I arrange a , b , c a,b,c keeping b b in first position, Then I get only 2 arrange, they are b c a , b a c bca,bac . It happens because I calculate it without b b .

Md Mehedi Hasan - 3 years, 6 months ago

see Kaan Berk Erdogmus's solution. I think his solution process is more clearer.

Md Mehedi Hasan - 3 years, 7 months ago

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