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Question

How many words, with or without meaning, can be formed using all the letters of the word EQUATION at a time so that the vowels and consonants occur together?

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Solution

The word EQUATION contains 8 different letters from which 5 are vowels and 3 are consonants i.e. E, U, A, I and O are vowels and Q, T and N are consonants. When all the vowels occur together, then it is considered to be 1 letter and when the consonants occur together then they are also considered as 1 letter. Then total letters will be 2. Therefore, the arrangement of the word is the number of permutation of 2 letters taken all at a time.

The formula to calculate the permutation is,

P n r = n! ( nr )!

Where n is the number of objects taken r at a time.

Substitute 2 for n and 2 for r in the above equation.

P 2 2 = 2! ( 22 )! = 2! 0! = 2! 1 =2!

The formula to calculate n! is defined as,

n!=1×2×3××( n1 )×n

Thus the factorial of 2 is,

P 2 2 =2×1 =2

Thus, the total numbers of words that can be formed are 2.

Since there are 5 vowels, thus they are also being arranged in themselves. The number of arrangements of vowels is the combination of 5 vowels taken all at a time.

The formula to calculate the permutation is,

P n r = n! ( nr )!

Where n is the number of objects taken r at a time.

Substitute 5 for n and 5 for r in the above equation.

P 5 5 = 5! ( 55 )! = 5! 0! = 5! 1 =5!

The formula to calculate n! is defined as,

n!=1×2×3××( n1 )×n

Thus the factorial of 5 is,

P 5 5 =5×4×3×2×1 =120

Thus, the total numbers of words that can be formed are 120.

Since there are 3 consonants, thus they are also being arranged in themselves. The number of arrangements of vowels is the combination of 3 consonants taken all at a time.

The formula to calculate the permutation is,

P n r = n! ( nr )!

Where n is the number of objects taken r at a time.

Substitute 3 for n and 3 for r in the above equation.

P 3 3 = 3! ( 33 )! = 3! 0! = 3! 1 =3!

The formula to calculate n! is defined as,

n!=1×2×3××( n1 )×n

Thus the factorial of 3 is,

P 3 3 =3×2×1 =6

Thus, the total numbers of words that can be formed are 6.

By multiplication principle which states that if an event can occur in m different ways and follows another event that can occur in n different ways, the number of ways that the words are selected is 2×120×6=1440 .


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