Question bank/JEE Main/Mathematics
JEE MainMathematics
A student guesses of each of 30 true/false questions. The chance
that he gets at least 15 correct, is
Show answer and solution
P(E) = 30C15 + 30C16 + 30C17 +.......+
30C30 ].......(1)
P(E) = 30C0 + 30C1 + 30C2 +.......+ 30C15 ].......(2)
(1) + (2)
2P(E) = 30C0 + 30C1 +.......+ 30C15 +
30C16 +.......+ 30C30 + 30C15]
30C30 ].......(1)
P(E) = 30C0 + 30C1 + 30C2 +.......+ 30C15 ].......(2)
(1) + (2)
2P(E) = 30C0 + 30C1 +.......+ 30C15 +
30C16 +.......+ 30C30 + 30C15]
Source: Grass-G / M-01 Mathematics Paper-1.docx
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