Arithmatical - Permutations and Combinations
DIRECTIONS : Problems based on Permutations.
21. |
In how many different ways can the letters of the word 'SOFTWARE' be arranged in such a way that the vowels always come together? |
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A. 720 |
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B. 360 |
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C. 1440 |
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D. 13440 |
Solution |
The word 'SOFTWARE' contains 8 letters. |
When the vowels OAE are always together, they can be supported to form one letter. |
Thus, we have to arrange the letters SFTWR (OAE). |
Now, 5 letters can be arranged in 6! = 720 ways. |
The vowels (OAE) can be arranged among themselves in 3! = 6 ways. |
Therefore required number of ways | = (720 x 6) |
= 4320. |
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22. |
Find the value of 10C3 |
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A. 30 |
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B. 60 |
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C. 90 |
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D. 120 |
Solution |
10C3 | = 10 x 9 x 8 / 3! |
= 10 x 9 x 8 / 3 x 2 x 1 |
= 120. |
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23. |
In how many different ways can the letters of the word ‘LEADING’ be arranged in such a way that the vowels always come together? |
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A. 360 |
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B. 480 |
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C. 530 |
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D. 720 |
Solution |
The word 'LEADING' contains 7 letters. |
When the vowels EAI are always together, they can be supported to form one letter. |
Then, we have to arrange the letters LDNG (EAI). |
Now, 5 letters can be arranged in 5! = 120 ways. |
The vowels (EAI) can be arranged among themselves in 3! = 6 ways. |
Therefore required number of ways | = (120 x 6) |
= 720. |
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