BdMO National Primary 2016/2

Discussion on Bangladesh Mathematical Olympiad (BdMO) National
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samiul_samin
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BdMO National Primary 2016/2

Unread post by samiul_samin » Thu Feb 15, 2018 11:04 am

$(11+11) \times(12+12)\times (13+13)...\times(18+18)\times(19+19)=x$

What is the remainder ,if $x$ is divided by $10$?

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Tasnood
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Re: BdMO National Primary 2016/2

Unread post by Tasnood » Thu Feb 15, 2018 4:16 pm

$(11+11) \times (12+12) \times (13+13) \times...\times (18+18) \times (19+19)=22 \times 24 \times 26 \times...\times 38$
Here, the fifth term will be: $(15+15)=30$ which is divisible by $10$
As $x=30 \times y$
So, $10|x$
Remainder=$0$
[Can't simplify more for primary :D ]

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samiul_samin
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Re: BdMO National Primary 2016/2

Unread post by samiul_samin » Thu Feb 15, 2018 8:10 pm

Tasnood wrote:
Thu Feb 15, 2018 4:16 pm
$(11+11) \times (12+12) \times (13+13) \times...\times (18+18) \times (19+19)=22 \times 24 \times 26 \times...\times 38$
Here, the fifth term will be: $(15+15)=30$ which is divisible by $10$
As $x=30 \times y$
So, $10|x$
Remainder=$0$
[Can't simplify more for primary :D ]
I was thinking about how to solve it simply.It is much more simple than my solution.

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