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BdMO National Primary 2016/2
Posted: Thu Feb 15, 2018 11:04 am
by samiul_samin
$(11+11) \times(12+12)\times (13+13)...\times(18+18)\times(19+19)=x$
What is the remainder ,if $x$ is divided by $10$?
Re: BdMO National Primary 2016/2
Posted: Thu Feb 15, 2018 4:16 pm
by Tasnood
$(11+11) \times (12+12) \times (13+13) \times...\times (18+18) \times (19+19)=22 \times 24 \times 26 \times...\times 38$
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 
]
Re: BdMO National Primary 2016/2
Posted: Thu Feb 15, 2018 8:10 pm
by samiul_samin
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 ]
I was thinking about how to solve it simply.It is much more simple than my solution.