Number of words that can be made using all the letters of the word W, if Os as well as Is are separated is?
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I am facing difficulty in solving the 18th Question from the above passage.
Attempt:
I have attempted it using principal of inclusion and exclusion.
Let n be the required number of ways.
$n = text{Total number of ways - Number of ways in which Os and Is are together}$
$implies n = dfrac{12!}{3!2!2!} - dfrac{11!}{2!3!} - dfrac{10!}{2!2!}+ dfrac{9!2!}{2!} = 399 times 8!$
This gives $N = 399$ which is wrong. Can you please tell me why am I getting the wrong answer?
combinatorics permutations combinations
$endgroup$
add a comment |
$begingroup$
I am facing difficulty in solving the 18th Question from the above passage.
Attempt:
I have attempted it using principal of inclusion and exclusion.
Let n be the required number of ways.
$n = text{Total number of ways - Number of ways in which Os and Is are together}$
$implies n = dfrac{12!}{3!2!2!} - dfrac{11!}{2!3!} - dfrac{10!}{2!2!}+ dfrac{9!2!}{2!} = 399 times 8!$
This gives $N = 399$ which is wrong. Can you please tell me why am I getting the wrong answer?
combinatorics permutations combinations
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$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago
add a comment |
$begingroup$
I am facing difficulty in solving the 18th Question from the above passage.
Attempt:
I have attempted it using principal of inclusion and exclusion.
Let n be the required number of ways.
$n = text{Total number of ways - Number of ways in which Os and Is are together}$
$implies n = dfrac{12!}{3!2!2!} - dfrac{11!}{2!3!} - dfrac{10!}{2!2!}+ dfrac{9!2!}{2!} = 399 times 8!$
This gives $N = 399$ which is wrong. Can you please tell me why am I getting the wrong answer?
combinatorics permutations combinations
$endgroup$
I am facing difficulty in solving the 18th Question from the above passage.
Attempt:
I have attempted it using principal of inclusion and exclusion.
Let n be the required number of ways.
$n = text{Total number of ways - Number of ways in which Os and Is are together}$
$implies n = dfrac{12!}{3!2!2!} - dfrac{11!}{2!3!} - dfrac{10!}{2!2!}+ dfrac{9!2!}{2!} = 399 times 8!$
This gives $N = 399$ which is wrong. Can you please tell me why am I getting the wrong answer?
combinatorics permutations combinations
combinatorics permutations combinations
asked 2 hours ago
AbcdAbcd
3,08931337
3,08931337
$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago
add a comment |
$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago
$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago
add a comment |
3 Answers
3
active
oldest
votes
$begingroup$
Your mistake is not noticing that the I's can be non-separated two different ways: We can have all three of them together as III, but we can also have II in one place and I in another.
One way to calculate how many ways this can happen is to think of one pair II as a single letter, and the third I as a separate letter, and count the number of words we can make. This will count each III case twice: Once as I II, and once as II I. So we have to subtract the number of such cases once.
With this correction, the final calculation becomes
$$
overbrace{frac{12!}{3!2!2!}}^{text{All words}} - overbrace{frac{11!}{3!2!}}^{text{O's not separate}} - overbrace{left(underbrace{frac{11!}{2!2!}}_{text{II and I}} - underbrace{frac{10!}{2!2!}}_{text{III}}right)}^{text{I's not separate}} + overbrace{left(underbrace{frac{10!}{2!}}_{text{OO, II and I}} - underbrace{frac{9!}{2!}}_{text{OO and III}}right)}^{text{Neither O's nor I's separate}}
$$
which turns out to be $8!cdot 228$.
$endgroup$
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
add a comment |
$begingroup$
The letter $I$ appears three times. You have calculated the number of ways to arrange the letters so that the three copies of $I$ aren't all in the same place (and also the two $O$s are separated). However, "separated" here means that no two of them are together. Your count includes such "words" as STIILOCATINO, which should be excluded.
$endgroup$
add a comment |
$begingroup$
How did you get each of the terms of $n$?
$frac{12!}{3!2!2!}$ : The number of ways of arranging the letters of SOLICITATION.
$frac{11!}{2!3!}$ : The number of ways in which the two $O$s can be together in SOLICITATION.
$frac{10!}{2!2!}$ : The number of ways in which the three $I$s can be together in SOLICITATION.
$frac{9!2!}{2!}$ : The number of ways in which the three $I$s and two $O$s can be together in SOLICITATION.
Well , the problem is this : the complement of this case, also includes the case where two $I$s can be together and the third can be separate. You have not neglected this case, and that's why you have an answer larger than the given answer.
$endgroup$
add a comment |
Your Answer
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3 Answers
3
active
oldest
votes
3 Answers
3
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
Your mistake is not noticing that the I's can be non-separated two different ways: We can have all three of them together as III, but we can also have II in one place and I in another.
One way to calculate how many ways this can happen is to think of one pair II as a single letter, and the third I as a separate letter, and count the number of words we can make. This will count each III case twice: Once as I II, and once as II I. So we have to subtract the number of such cases once.
With this correction, the final calculation becomes
$$
overbrace{frac{12!}{3!2!2!}}^{text{All words}} - overbrace{frac{11!}{3!2!}}^{text{O's not separate}} - overbrace{left(underbrace{frac{11!}{2!2!}}_{text{II and I}} - underbrace{frac{10!}{2!2!}}_{text{III}}right)}^{text{I's not separate}} + overbrace{left(underbrace{frac{10!}{2!}}_{text{OO, II and I}} - underbrace{frac{9!}{2!}}_{text{OO and III}}right)}^{text{Neither O's nor I's separate}}
$$
which turns out to be $8!cdot 228$.
$endgroup$
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
add a comment |
$begingroup$
Your mistake is not noticing that the I's can be non-separated two different ways: We can have all three of them together as III, but we can also have II in one place and I in another.
One way to calculate how many ways this can happen is to think of one pair II as a single letter, and the third I as a separate letter, and count the number of words we can make. This will count each III case twice: Once as I II, and once as II I. So we have to subtract the number of such cases once.
With this correction, the final calculation becomes
$$
overbrace{frac{12!}{3!2!2!}}^{text{All words}} - overbrace{frac{11!}{3!2!}}^{text{O's not separate}} - overbrace{left(underbrace{frac{11!}{2!2!}}_{text{II and I}} - underbrace{frac{10!}{2!2!}}_{text{III}}right)}^{text{I's not separate}} + overbrace{left(underbrace{frac{10!}{2!}}_{text{OO, II and I}} - underbrace{frac{9!}{2!}}_{text{OO and III}}right)}^{text{Neither O's nor I's separate}}
$$
which turns out to be $8!cdot 228$.
$endgroup$
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
add a comment |
$begingroup$
Your mistake is not noticing that the I's can be non-separated two different ways: We can have all three of them together as III, but we can also have II in one place and I in another.
One way to calculate how many ways this can happen is to think of one pair II as a single letter, and the third I as a separate letter, and count the number of words we can make. This will count each III case twice: Once as I II, and once as II I. So we have to subtract the number of such cases once.
With this correction, the final calculation becomes
$$
overbrace{frac{12!}{3!2!2!}}^{text{All words}} - overbrace{frac{11!}{3!2!}}^{text{O's not separate}} - overbrace{left(underbrace{frac{11!}{2!2!}}_{text{II and I}} - underbrace{frac{10!}{2!2!}}_{text{III}}right)}^{text{I's not separate}} + overbrace{left(underbrace{frac{10!}{2!}}_{text{OO, II and I}} - underbrace{frac{9!}{2!}}_{text{OO and III}}right)}^{text{Neither O's nor I's separate}}
$$
which turns out to be $8!cdot 228$.
$endgroup$
Your mistake is not noticing that the I's can be non-separated two different ways: We can have all three of them together as III, but we can also have II in one place and I in another.
One way to calculate how many ways this can happen is to think of one pair II as a single letter, and the third I as a separate letter, and count the number of words we can make. This will count each III case twice: Once as I II, and once as II I. So we have to subtract the number of such cases once.
With this correction, the final calculation becomes
$$
overbrace{frac{12!}{3!2!2!}}^{text{All words}} - overbrace{frac{11!}{3!2!}}^{text{O's not separate}} - overbrace{left(underbrace{frac{11!}{2!2!}}_{text{II and I}} - underbrace{frac{10!}{2!2!}}_{text{III}}right)}^{text{I's not separate}} + overbrace{left(underbrace{frac{10!}{2!}}_{text{OO, II and I}} - underbrace{frac{9!}{2!}}_{text{OO and III}}right)}^{text{Neither O's nor I's separate}}
$$
which turns out to be $8!cdot 228$.
edited 21 mins ago
answered 1 hour ago
ArthurArthur
120k7120204
120k7120204
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
add a comment |
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
Thanks for the answer I have understood my mistake, but I am unable to understand the final equation in your answer. Can you label the terms like which term stands for which case?
$endgroup$
– Abcd
32 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
$begingroup$
@Abcd I added a short explanation for what each term represents. The basic structure of your inclusion-exclusion calculation is still there, just with the two last terms corrected to make up for the mistake.
$endgroup$
– Arthur
21 mins ago
add a comment |
$begingroup$
The letter $I$ appears three times. You have calculated the number of ways to arrange the letters so that the three copies of $I$ aren't all in the same place (and also the two $O$s are separated). However, "separated" here means that no two of them are together. Your count includes such "words" as STIILOCATINO, which should be excluded.
$endgroup$
add a comment |
$begingroup$
The letter $I$ appears three times. You have calculated the number of ways to arrange the letters so that the three copies of $I$ aren't all in the same place (and also the two $O$s are separated). However, "separated" here means that no two of them are together. Your count includes such "words" as STIILOCATINO, which should be excluded.
$endgroup$
add a comment |
$begingroup$
The letter $I$ appears three times. You have calculated the number of ways to arrange the letters so that the three copies of $I$ aren't all in the same place (and also the two $O$s are separated). However, "separated" here means that no two of them are together. Your count includes such "words" as STIILOCATINO, which should be excluded.
$endgroup$
The letter $I$ appears three times. You have calculated the number of ways to arrange the letters so that the three copies of $I$ aren't all in the same place (and also the two $O$s are separated). However, "separated" here means that no two of them are together. Your count includes such "words" as STIILOCATINO, which should be excluded.
answered 1 hour ago
jmerryjmerry
16.6k11633
16.6k11633
add a comment |
add a comment |
$begingroup$
How did you get each of the terms of $n$?
$frac{12!}{3!2!2!}$ : The number of ways of arranging the letters of SOLICITATION.
$frac{11!}{2!3!}$ : The number of ways in which the two $O$s can be together in SOLICITATION.
$frac{10!}{2!2!}$ : The number of ways in which the three $I$s can be together in SOLICITATION.
$frac{9!2!}{2!}$ : The number of ways in which the three $I$s and two $O$s can be together in SOLICITATION.
Well , the problem is this : the complement of this case, also includes the case where two $I$s can be together and the third can be separate. You have not neglected this case, and that's why you have an answer larger than the given answer.
$endgroup$
add a comment |
$begingroup$
How did you get each of the terms of $n$?
$frac{12!}{3!2!2!}$ : The number of ways of arranging the letters of SOLICITATION.
$frac{11!}{2!3!}$ : The number of ways in which the two $O$s can be together in SOLICITATION.
$frac{10!}{2!2!}$ : The number of ways in which the three $I$s can be together in SOLICITATION.
$frac{9!2!}{2!}$ : The number of ways in which the three $I$s and two $O$s can be together in SOLICITATION.
Well , the problem is this : the complement of this case, also includes the case where two $I$s can be together and the third can be separate. You have not neglected this case, and that's why you have an answer larger than the given answer.
$endgroup$
add a comment |
$begingroup$
How did you get each of the terms of $n$?
$frac{12!}{3!2!2!}$ : The number of ways of arranging the letters of SOLICITATION.
$frac{11!}{2!3!}$ : The number of ways in which the two $O$s can be together in SOLICITATION.
$frac{10!}{2!2!}$ : The number of ways in which the three $I$s can be together in SOLICITATION.
$frac{9!2!}{2!}$ : The number of ways in which the three $I$s and two $O$s can be together in SOLICITATION.
Well , the problem is this : the complement of this case, also includes the case where two $I$s can be together and the third can be separate. You have not neglected this case, and that's why you have an answer larger than the given answer.
$endgroup$
How did you get each of the terms of $n$?
$frac{12!}{3!2!2!}$ : The number of ways of arranging the letters of SOLICITATION.
$frac{11!}{2!3!}$ : The number of ways in which the two $O$s can be together in SOLICITATION.
$frac{10!}{2!2!}$ : The number of ways in which the three $I$s can be together in SOLICITATION.
$frac{9!2!}{2!}$ : The number of ways in which the three $I$s and two $O$s can be together in SOLICITATION.
Well , the problem is this : the complement of this case, also includes the case where two $I$s can be together and the third can be separate. You have not neglected this case, and that's why you have an answer larger than the given answer.
answered 1 hour ago
астон вілла олоф мэллбэргастон вілла олоф мэллбэрг
40k33477
40k33477
add a comment |
add a comment |
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$begingroup$
How do you know that your solution is wrong? There is also option (D)
$endgroup$
– Robert Z
1 hour ago
$begingroup$
@RobertZ answer given is option B
$endgroup$
– Abcd
1 hour ago