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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,608

A visitor has asked me by email:

I need a solution for the below questions:

Can you write 31 by usingly only digit 3 five times?

Can you place 10 coins in a five straight lines each having four coins?

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

Well, the second one is a star:

O

O O O O

O O

O

O O

It would work if I could draw better, but you see what I mean.

The first one I'll have to think about.

Why did the vector cross the road?

It wanted to be normal.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,608

3^3 + 3 + 3/3 = 27 + 3 + 1 = 31

(That star would make a good logo !)

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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**wcy****Member**- Registered: 2005-08-04
- Posts: 117

Another way:

33-3+3/3=33-3+1=31

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**mathsyperson****Moderator**- Registered: 2005-06-22
- Posts: 4,900

Technically, the answer to both is 'yes'.

Why did the vector cross the road?

It wanted to be normal.

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**MathsIsFun****Administrator**- Registered: 2005-01-21
- Posts: 7,608

And I thought the answer to both was 31 ... silly me.

"The physicists defer only to mathematicians, and the mathematicians defer only to God ..." - Leon M. Lederman

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