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JEE Main 201815 AprilMorning ShiftOnline

Exam: JEE Main
Year: 2018
Date: 15 April
Shift: Morning Shift
Mode: Online
Subject: Mathematics
Chapter: Permutation and Combination

JEE Main 2018 · 15 April · Morning Shift · Online · Mathematics · Permutation and Combination

n - digit numbers are formed using only three digits 2,5 and 7 ....

n

- digit numbers are formed using only three digits 2,5 and 7 . The smallest value of

n

for which 900 such distinct numbers can be formed, is

Options

A6
B8
C9
D7

Correct answer

D. 7

Step-by-step solution

Required

n

digit numbers is

3^n

as each place can be filled by

2,5,7

. So smallest value of

n

such that

3^n>900

. Therefore

n=7

.

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