KVPY 2019 SB SX Exam Previous Papers

Question : 1 of 120

Marks: +1, -0

PART-I

MATHEMATICS

The number of four-letter words that can be formed with letters a, b, c such that all three letters occur is

Solution:

ways =

3^4 -^3C_1 . 2^4 + ^3C_2. 1^4

= 81 -48 + 3 = 36

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