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Question Number 162118 by SANOGO last updated on 27/Dec/21

determiner le reste de la division euclidienne de  10^(100)  par 105

$${determiner}\:{le}\:{reste}\:{de}\:{la}\:{division}\:{euclidienne}\:{de} \\ $$$$\mathrm{10}^{\mathrm{100}} \:{par}\:\mathrm{105} \\ $$

Commented by SANOGO last updated on 27/Dec/21

thank you

$${thank}\:{you} \\ $$

Commented by SANOGO last updated on 27/Dec/21

merci bien

$${merci}\:{bien} \\ $$

Commented by mr W last updated on 27/Dec/21

in following stupid method   with “=^R ” i mean  “has the same remainder as”.  10^(100) =10×10^(99) =10×(1000)^(33)   =10×(9×105+55)^(33)   =^R 10×55^(33) =10×55×(3025)^(16)   =10×55×(28×105+85)^(16)   =^R 10×55×85^(16) =10×55×(68×105+85)^8   =^R 10×55×85^8   =^R 10×55×85^4   =^R 10×55×85^2   =^R 10×55×85  =^R 25  i.e. the remainder is 25 when 10^(100)   is divided by 105.

$${in}\:{following}\:{stupid}\:{method}\: \\ $$$${with}\:``\overset{{R}} {=}''\:{i}\:{mean} \\ $$$$``{has}\:{the}\:{same}\:{remainder}\:{as}''. \\ $$$$\mathrm{10}^{\mathrm{100}} =\mathrm{10}×\mathrm{10}^{\mathrm{99}} =\mathrm{10}×\left(\mathrm{1000}\right)^{\mathrm{33}} \\ $$$$=\mathrm{10}×\left(\mathrm{9}×\mathrm{105}+\mathrm{55}\right)^{\mathrm{33}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}^{\mathrm{33}} =\mathrm{10}×\mathrm{55}×\left(\mathrm{3025}\right)^{\mathrm{16}} \\ $$$$=\mathrm{10}×\mathrm{55}×\left(\mathrm{28}×\mathrm{105}+\mathrm{85}\right)^{\mathrm{16}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}×\mathrm{85}^{\mathrm{16}} =\mathrm{10}×\mathrm{55}×\left(\mathrm{68}×\mathrm{105}+\mathrm{85}\right)^{\mathrm{8}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}×\mathrm{85}^{\mathrm{8}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}×\mathrm{85}^{\mathrm{4}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}×\mathrm{85}^{\mathrm{2}} \\ $$$$\overset{{R}} {=}\mathrm{10}×\mathrm{55}×\mathrm{85} \\ $$$$\overset{{R}} {=}\mathrm{25} \\ $$$${i}.{e}.\:{the}\:{remainder}\:{is}\:\mathrm{25}\:{when}\:\mathrm{10}^{\mathrm{100}} \\ $$$${is}\:{divided}\:{by}\:\mathrm{105}. \\ $$

Commented by Rasheed.Sindhi last updated on 27/Dec/21

∨ ∩i⊂∈ sir!   If your ′stupid′ method is so wonderful  what your ′wonderful′ method will be!!!

$$\vee\:\cap\mathrm{i}\subset\in\:\boldsymbol{\mathrm{sir}}!\: \\ $$$${If}\:{your}\:'{stupid}'\:{method}\:{is}\:{so}\:{wonderful} \\ $$$${what}\:{your}\:'{wonderful}'\:{method}\:{will}\:{be}!!! \\ $$

Commented by Rasheed.Sindhi last updated on 27/Dec/21

The following method also works well:  x≡y(mod 6)_(x & y have_(same remainder_(on dividing 6) )  ) ⇒10^x ≡10^y (mod 105)_(10^x &10^y  have_(same remainder_(on dividing 105) ) )   ⇒10^(6x+k) ≡10^k       10^(100) =10^(6×16+4) ≡10^4 ≡25(mod 105)

$$\mathcal{T}{he}\:{following}\:{method}\:{also}\:{works}\:{well}: \\ $$$$\underset{\underset{\underset{{on}\:{dividing}\:\mathrm{6}} {{same}\:{remainder}}} {{x}\:\&\:{y}\:{have}}\:} {{x}\equiv{y}\left({mod}\:\mathrm{6}\right)}\Rightarrow\underset{\underset{\underset{{on}\:{dividing}\:\mathrm{105}} {{same}\:{remainder}}} {\mathrm{10}^{{x}} \&\mathrm{10}^{{y}} \:{have}}} {\mathrm{10}^{{x}} \equiv\mathrm{10}^{{y}} \left({mod}\:\mathrm{105}\right)} \\ $$$$\Rightarrow\mathrm{10}^{\mathrm{6}{x}+{k}} \equiv\mathrm{10}^{{k}} \\ $$$$\:\:\:\:\mathrm{10}^{\mathrm{100}} =\mathrm{10}^{\mathrm{6}×\mathrm{16}+\mathrm{4}} \equiv\mathrm{10}^{\mathrm{4}} \equiv\mathrm{25}\left({mod}\:\mathrm{105}\right) \\ $$

Commented by mr W last updated on 27/Dec/21

this is a smart method!

$${this}\:{is}\:{a}\:{smart}\:{method}! \\ $$

Commented by Rasheed.Sindhi last updated on 27/Dec/21

Thanks sir!

$$\mathbb{T}\mathrm{han}\Bbbk\mathrm{s}\:\boldsymbol{\mathrm{sir}}! \\ $$

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