Math Is Fun Forum
  Discussion about math, puzzles, games and fun.   Useful symbols: √ ∞ ≠ ≤ ≥ ≈ ⇒ ∈ Δ θ ∴ ∑ ∫ π -

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Topic review (newest first)

cooljackiec
2013-01-23 11:02:13

Thank you

bobbym
2013-01-22 12:24:26

Hi;

You do not have to do much counting. Spot the pattern works well here.

I am getting 4.5 x 10 ^19 numbers.

cooljackiec
2013-01-22 08:25:37

That doesn't help, I knew that just that i keep losing count.

muxdemux
2013-01-22 05:42:14

I could only figure out that there's at least

.

cooljackiec
2013-01-22 04:13:22

How many 20-digit numbers are such that the sum of their digits is even?

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