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If letters may repeat, the number of four letter words from R, O, S and E becomes:
A64
B128
C256
D24
Answer & Solution
Correct answer: C. 256
1. Each of the 4 places has 4 choices.
2. That is 4 multiplied by itself four times.
3. The count is 256.
_Source: NCERT Class 11 Mathematics, Chapter 7, Permutations and Combinations._
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