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I just started using Mathematica and at the moment I'm learning some things.

As you can see in the headline, I want to make a list of numbers (up to 100) whose digit sum is greater or equal 5.

I started with

Select[Total[IntegerDigits[Range[100]], {2}], GreaterThan[4]]

that leads to the following list:

{5, 6, 7, 8, 9, 5, 6, 7, 8, 9, 10, 5, 6, 7, 8, 9, 10, 11, 5, 6, 7, 8, \
9, 10, 11, 12, 5, 6, 7, 8, 9, 10, 11, 12, 13, 5, 6, 7, 8, 9, 10, 11, \
12, 13, 14, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 7, 8, 9, 10, 11, 12, \
13, 14, 15, 16, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 9, 10, 11, 12, \
13, 14, 15, 16, 17, 18}

So now I have the list of all digit sums meeting my requirement. But how do I use it to list up the numbers which belong to them? I wanted to use it to overwrite the "wrong" numbers with a "nothing". Or am I using a much too difficult way?

Thank you in advance! I hope my English is good enough to at least understand what I want to do

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    $\begingroup$ Select[Range[100], Total@IntegerDigits@# > 4 &] $\endgroup$
    – Bob Hanlon
    Jun 16, 2020 at 16:22
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    $\begingroup$ Yet another way: x /. FindInstance[Mod[x, 10] + Quotient[x, 10] >= 5 && 0 <= x < 100, x, Integers, 100] $\endgroup$
    – flinty
    Jun 16, 2020 at 17:15

1 Answer 1

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With[{ints = Range[100]},
 Pick[ints, Clip[Total[IntegerDigits[ints], {2}], {-∞, 5}], 5]]

Using Nothing:

With[{ints = Range[100]},
 ints /. Thread[PositionIndex[Clip[Total[IntegerDigits[ints], {2}], {4, ∞}]][4] -> Nothing]]
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  • $\begingroup$ Thanks! Is there a way using "nothing" to replace that, too? Or is it much too complicate? $\endgroup$
    – Beggi01
    Jun 16, 2020 at 16:12
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    $\begingroup$ @Beggi01 Added a nothing version $\endgroup$
    – Coolwater
    Jun 16, 2020 at 16:24
  • $\begingroup$ Can't use the option to thank you - so: Thank you very much! $\endgroup$
    – Beggi01
    Jun 16, 2020 at 16:42

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