The question asks me to prove that if I have 5 arbitrary natural numbers to show that one of the sums (in order) is divisible by 5. So say the numbers are [itex]a_1,a_2,a_3,a_4,a_5[/itex] some examples would be:(adsbygoogle = window.adsbygoogle || []).push({});

[tex]a_1 + a_2 + a_3[/tex]

[tex]a_4[/tex]

[tex]a_3 + a_4[/tex]

etc..

My first thought was to consider the remainder upon division 5 and then start identifying all the possible combinations where the sum is divisible by 5 and show there are no more left. However when starting this I realised this was actually a lot of work and there must be some simpler way. Can anyone else point me in a different direction?

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# Homework Help: Sum divisable by 5.

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