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Given the numbers $1$, $5$, $7$, $8$, and $9$, how many $3$-digit numbers larger than $700$ can be formed if repetition is not allowed?
The answer is $36$.
I want a detailed explanation please of how we get this answer?
asked Apr 15, 2017 at 13:53
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Let your number be $ABC$,
$A $ can take up values 7,8 and 9 i.e. total 3. Now $B$ has total 4 choices and simultaneously $C$ will have 3.
Thus answer=4*3*3=36
Example: Let $A$=7. Thus $B$ is left with {1,5,8,9}.
Let $B$ be 5. Thus now $C$ is left with {1,8,9}. Clear?
answered Apr 15, 2017 at 13:56
The Dead LegendThe Dead Legend
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How many numbers of 3 digits can be formed with the digits 5,6,7,8,9 repetition of the digits not allowed?
Question
A
30
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B
60
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C
120
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D
240
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Solution
The correct option is B
60
=5×4×3=60
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Q.
How many 3-digit numbers can be formed from the digits 1, 2, 3, 4 and 5 assuming that
[i] repetition of the digits is allowed?
[ii] repetition of the digits is not allowed?