Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

Pages: **1**

**cooljackiec****Member**- Registered: 2012-12-13
- Posts: 178

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

I see you have graph paper.

You must be plotting something

Offline

**muxdemux****Member**- Registered: 2012-12-23
- Posts: 80

I could only figure out that there's at least

.*Last edited by muxdemux (2013-01-21 06:42:30)*

Offline

**cooljackiec****Member**- Registered: 2012-12-13
- Posts: 178

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

I see you have graph paper.

You must be plotting something

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 95,975

Hi;

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

I am getting 4.5 x 10 ^19 numbers.

**In mathematics, you don't understand things. You just get used to them.**

**If it ain't broke, fix it until it is.**

Offline

**cooljackiec****Member**- Registered: 2012-12-13
- Posts: 178

Thank you

I see you have graph paper.

You must be plotting something

Offline

Pages: **1**