Question:
The number of three digit numbers in which $9$ appears only in one place is
The number of three digit numbers in which $9$ appears only in one place is
Updated On: Apr 4, 2024
- 243
- 234
- 217
- 225
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The Correct Option is D
Solution and Explanation
The number of three digit numbers in which 9 appears at hundred place only is $=1 \times 9 \times 9=81$ Similarly, the number of three digit numbers in which 9 appears at ten or unit place only is
$=(8 \times 1 \times 9) \times 2=144$
So, required number $=81+144=225$
$=(8 \times 1 \times 9) \times 2=144$
So, required number $=81+144=225$
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Concepts Used:
Permutations
A permutation is an arrangement of multiple objects in a particular order taken a few or all at a time. The formula for permutation is as follows:
\(^nP_r = \frac{n!}{(n-r)!}\)
nPr = permutation
n = total number of objects
r = number of objects selected
Types of Permutation
- Permutation of n different things where repeating is not allowed
- Permutation of n different things where repeating is allowed
- Permutation of similar kinds or duplicate objects