Maths-
General
Easy
Question
A five letter word is to be formed such that the letters appearing in the odd numbered positions are taken from the letters which appear without repetition in the word 'MATHEMATICS'. Further the letters appearing in the even numbered positions are taken from the letters which appear with repetitions in the same word MATHEMATICS. In how many different ways the five letter word can be formed -
- 390
- 600
- 540
- 450
The correct answer is: 540
In word MATHEMATICS
H, E, C, I and S – without repetition
M, A, T – occurs twice 5 letters can be placed on 3 places in 5P3 ways.
Again even places 2nd & 4th position can be filled by the three letter M, A & T
Even places can be filled in two ways
3C1 ways
3C1 × 2! ways
Total ways 3C1 + 3C1 × 2! = 9 ways
Required number of ways = 5P3 × 9 = 540 ways.
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