How many numbers can be formed with the digits 3,4,5,6,7 which are greater than 1000(repetition is not allowed) ?i think 2 parts will be there.first from 1000 to 9999.next from 10000 and above.i could not get the correct answer
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2$\binom{5}{4}4!+5!=2\cdot5!=240$. – Alexander Burstein Dec 28 '17 at 07:17
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Yes,
Case 1: $n=\overline{abcd}$
Because every digit in $\{3,4,5,6,7\}$ is $>1$, we can select $\binom{5}{4}=5$ $4-$tuples. Each tuple can be ordened in $4!=24$ ways.
Case 2: $n=\overline{abcde}$
Here we have $5!=120$ numbers.
Total of cases: $5\times 24+120=240$ numbers.
Martín Vacas Vignolo
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