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The number of natural numbers less than 500 in which no two digits are repeated is
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$378$
Number of 3 digit natural number less than 500 in which no two digits are repeated $=4 \times 9 \times 8=288$
4 ways $=4$ number $(1,2,3,4)$
Now number of 2 digit natural numbers less than 500 in which no. of two digits are repeated $=9 \times 9=81$
Now number of 1 digit natural number less than $500=9$
Therefore required number of digits $=288+81+9=378$
4 ways $=4$ number $(1,2,3,4)$
Now number of 2 digit natural numbers less than 500 in which no. of two digits are repeated $=9 \times 9=81$
Now number of 1 digit natural number less than $500=9$
Therefore required number of digits $=288+81+9=378$
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