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 #4
avatar+170 
+3

D**n, multiplication seemed logical to me, nevertheless this should be able to be figured out as well.

 

The last number is relatively easy since it's the result of $${{\mathtt{2}}}^{{\mathtt{n}}}$$, which means the last digit regularly skips between this array of numbers: 2,4,8,6.

 

For $${{\mathtt{2}}}^{\left({\mathtt{4}}{n}\right)}$$ the last digit is 6.

 

For $${{\mathtt{2}}}^{\left({\mathtt{4}}{n}{\mathtt{\,\small\textbf+\,}}{\mathtt{1}}\right)}$$ the last digit is 2.

 

For $${{\mathtt{2}}}^{\left({\mathtt{4}}{n}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}\right)}$$ the last digit is 4.

 

For $${{\mathtt{2}}}^{\left({\mathtt{4}}{n}{\mathtt{\,\small\textbf+\,}}{\mathtt{3}}\right)}$$ the last digit is 8.

 

We know the last digit is multiplied 1122 times, $${\frac{{\mathtt{1\,122}}}{{\mathtt{4}}}} = {\frac{{\mathtt{561}}}{{\mathtt{2}}}} = {\mathtt{280.5}}$$ so it is of the form $${{\mathtt{2}}}^{\left({\mathtt{4}}{n}{\mathtt{\,\small\textbf+\,}}{\mathtt{2}}\right)}$$ which means the last digit is 4.

 

While doing this I figured out a better way to solve this problem, we know this of the exponent:

 

$${\mathtt{1\,122}} = {\mathtt{2}}{\mathtt{\,\times\,}}{\mathtt{3}}{\mathtt{\,\times\,}}{\mathtt{11}}{\mathtt{\,\times\,}}{\mathtt{17}}$$

 

Another thing we know for sure is that while multiplying two numbers only the last two digits of each number affect the last two digits of the answer. Hence all digits save for the last two are irrelevant for further multiplication.

 

Since only the last two digits matter of the 1122 being multiplied we can drop the first two digits:

$${{\mathtt{22}}}^{{\mathtt{1\,122}}} = \left({\left({\left({\left({{\mathtt{22}}}^{{\mathtt{2}}}\right)}^{{\mathtt{3}}}\right)}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}}\right)$$

$${\left({\left({{\mathtt{484}}}^{{\mathtt{3}}}\right)}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}}$$

 

Only last two digits matter

 

$${\left({\left({{\mathtt{84}}}^{{\mathtt{3}}}\right)}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}}$$

 

$${\left({{\mathtt{592\,704}}}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}}$$

 

Only last two digits matter

 

$${\left({{\mathtt{4}}}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}}$$

 

$${\left({{\mathtt{4}}}^{{\mathtt{11}}}\right)}^{{\mathtt{17}}} = {\left({\mathtt{4\,194\,304}}\right)}^{{\mathtt{17}}}$$

 

Only last two digits matter

 

$${{\mathtt{4}}}^{{\mathtt{17}}}$$

 

$${{\mathtt{4}}}^{{\mathtt{17}}} = {{\mathtt{4}}}^{{\mathtt{11}}}{\mathtt{\,\times\,}}{{\mathtt{4}}}^{{\mathtt{6}}} = {\mathtt{4\,194\,304}}{\mathtt{\,\times\,}}{{\mathtt{4}}}^{{\mathtt{6}}}$$

 

Only last two digits matter

 

$${\mathtt{4}}{\mathtt{\,\times\,}}{{\mathtt{4}}}^{{\mathtt{6}}} = {{\mathtt{4}}}^{{\mathtt{7}}} = {\mathtt{16\,384}}$$

 

Last two digits of $${{\mathtt{1\,122}}}^{{\mathtt{1\,122}}}$$ are 84, case closed.

Sep 1, 2014
 #1
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+5
Sep 1, 2014
 #1
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+5
Sep 1, 2014
 #101
avatar+118723 
0

Tues 2/9/14

*1) Finding the last 2 digits of a large power or a multiple.   Some very impressive number work here (Thanks Honga)

http://web2.0calc.com/questions/find-the-last-two-digit-of-1122-1122

2) Rotational Speed of a propeller 

http://web2.0calc.com/questions/an-airplane-propeller-rotates-1000-times-per-min-find-the-number-of-degrees-that-a-point-on-the-edge-of-the-propeller-will-rotate-in-1-sec

*3) Probability, quadratics, ducks and geese.  It doesn't get any better than this! lol

http://web2.0calc.com/questions/probability-help-needed-thx

*4) Trig Proof - More  impressive solutions from Bertie and Heurka (Thanks guys)

http://web2.0calc.com/questions/geometry_926#r0

  ♬                                        ♬ ♬ MELODY ♬ ♬                           ♫♪ You light up my life ♪ ♫ 

Sep 1, 2014
 #271
avatar+118723 
+6

@@ End of Day Wrap:    Mon 1/9/14       Sydney, Australia      Time 1:30am (Really Tuesday morning)     ♬

 

Hi all,

Today our great answers were supplied by CPhill, AzizHusain, Bertie, Honga, Heureka and TakahiroMaeda.  A very big thank you to each of you.  

 

Now straight to our interest posts:

 

1) This one looks interesting.

http://web2.0calc.com/questions/geometry_926

2) A log/exponential simplification.

http://web2.0calc.com/questions/1-2x-1-2-2xe-x-ln-3x-2-2

3) A little theory:   Fermat's last theorem.

http://web2.0calc.com/questions/fermat-s-last-theorem

4) How do you simplify a surd.  This is for our younger members.   

 http://web2.0calc.com/questions/please-help-what-is-the-simpliefied-form-of-radic-96-answer-needs-to-be-in-radical-form

5) Good little puzzle question

 http://web2.0calc.com/questions/i-am-a-3-digit-number-less-than-300-i-am-divisible-by-2-and-5-but-not-by-3-sum-of-my-digit-is-11-what-number-am-i

*6) Trigonometry - what could the answer be? 

http://web2.0calc.com/questions/in-triangle-abc-if-ac-is-12-bc-is-11-and-angle-a-is-30-angle-c-could-be-what

*7) Find the height of the triangle - A good one for our rug rats.  (said with great affection)

http://web2.0calc.com/questions/a-triangle-has-an-area-of-72-square-inches-if-the-base-of-the-triangle-has-a-length-of-18-inches-what-is-the-height-of-the-triangle-use-t#rr2

 

That is it for tonight.  Thanks everyone.    

 

            ♫♪  ♪ ♫                                 ♬ ♬ MELODY ♬ ♬                                  ♫♪  ♪ ♫ 

Sep 1, 2014
 #11
avatar+118723 
0
Sep 1, 2014

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