[ [Decimal numeral system ]

From the number 1234567...5657585960, remove 100 digits so that the remaining number is: a) the smallest; b) the largest.

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a) Since we need to find the smallest number, we cross out the 100 largest digits so that the number starts with zeros. The original number contains 111 digits, so 11 digits will remain: $00000123450=123450$.

b) The largest number starts with the largest number of nines (there can be no more than five), which are from the first five tens. The sixth digit should be the largest of those followed by at least five more digits. Such a digit is 7.