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Find the number of ways letters of the word HISTORY can be arranged if Y and T are together. - Mathematics and Statistics

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Sum

Find the number of ways letters of the word HISTORY can be arranged if Y and T are together.

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Solution

There are 7 letters in the word HISTORY
When ‘Y’ and ‘T’ are together.
Let us consider ‘Y’ and ‘T’ as one unit
This unit with the other 5 letters is to be arranged.
∴ The number of arrangements of one unit and 5 letters = 6P6 = 6!
Also, ‘Y’ and ‘T’ can be arranged among themselves in 2P2 i.e., 2! ways.
∴ Total number of arrangements when Y and T are always together = 6! × 2! = 720 × 2 = 1440
∴ 1440 words can be formed if Y and T are together.

Concept: Permutations - Permutations When Repetitions Are Allowed
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APPEARS IN

Balbharati Mathematics and Statistics 2 (Commerce) 11th Standard HSC Maharashtra State Board
Chapter 6 Permutations and Combinations
Exercise 6.3 | Q 8. (i) | Page 81
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