400 Day Streak Special

Algebra Level 3

( 1 + 1 2 + 1 3 + 1 4 + 1 5 ) e i π det ( 8 47 14 43 ) 1460 m o d 121 log 3 ( 59049 ) + v = 400 \large \left( 1+ \frac{1}{2+\frac{1}{3+\frac{1}{4+\frac{1}{5}}}} \right) e^{i\pi} \det \begin{pmatrix}8 & 47 \\ 14 & 43 \end{pmatrix} \frac{1460\bmod{121}}{\log_{3}(59049)} + v = 400

Find v v .


The answer is 40.

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2 solutions

X X
Jul 2, 2018

1 + 1 2 + 1 3 + 1 4 + 1 5 = 225 157 1+ \cfrac{1}{2+\cfrac{1}{3+\cfrac{1}{4+\cfrac{1}{5}}}}=\dfrac{225}{157}

e i π = 1 e^{i\pi}=-1

det ( 8 47 14 43 ) = 8 × 43 47 × 14 = 314 \text{det}\begin{pmatrix}8 & 47 \\ 14 & 43 \end{pmatrix}=8\times43-47\times14=-314

1460 ( m o d 121 ) = 8 1460\pmod {121}=8

log 3 ( 59049 ) = log 3 ( 3 10 ) = 10 \log_{3}(59049)=\log_{3}(3^{10})=10

The equation becomes 225 157 × ( 1 ) × ( 314 ) × 8 10 + v = 360 + v = 400 , v = 40 \dfrac{225}{157}\times(-1)\times(-314)\times\dfrac8{10}+v=360+v=400,v=40

@X X it's been around 2 years since i posted this problem....finally someone write a solution.

Ravneet Singh - 2 years, 11 months ago

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I saw this problem on the list of "need solution",so I decided to post a solution to it.Wow,2 years...

X X - 2 years, 11 months ago

From what is given, we have:

v = 400 ( 1 + 1 2 + 1 3 + 1 4 + 1 5 ) e i π det ( 8 47 14 43 ) 1460 m o d 121 log 3 59049 By Euler’s formula = 400 ( 1 + 1 2 + 1 3 + 5 21 ) ( cos π + i sin π ) ( 8 × 43 47 × 14 ) 250 m o d 121 log 3 ( 3 2 × 6561 ) = 400 ( 1 + 1 2 + 21 68 ) ( 1 ) ( 344 658 ) 8 log 3 ( 3 4 × 729 ) = 400 ( 1 + 68 157 ) ( 1 ) ( 314 ) 8 log 3 ( 3 6 × 81 ) = 400 225 157 × 314 × 8 log 3 ( 3 10 ) = 400 225 157 × 314 × 8 10 = 400 360 = 40 \begin{aligned} v & = 400 - \left(1+\frac 1{2+\frac 1{3+\frac 1{4+\frac 15}}}\right){\color{#3D99F6}e^{i\pi}}\det \begin{pmatrix} 8 & 47 \\ 14 & 43 \end{pmatrix} \frac {1460 \bmod 121}{\log_3 59049} & \small \color{#3D99F6} \text{By Euler's formula} \\ & = 400 - \left(1+\frac 1{2+\frac 1{3+\frac 5{21}}}\right) {\color{#3D99F6}\left(\cos \pi + i \sin \pi\right)} (8\times 43-47 \times 14) \frac {250 \bmod 121}{\log_3 (3^2\times 6561)} \\ & = 400 - \left(1+\frac 1{2+\frac {21}{68}} \right) (-1) (344-658) \frac 8{\log_3 (3^4\times 729)} \\ & = 400 - \left(1+\frac {68}{157} \right) (-1) (-314) \frac 8{\log_3 (3^6\times 81)} \\ & = 400 - \frac {225}{157} \times 314 \times \frac 8{\log_3 (3^{10})} \\ & = 400 - \frac {225}{157} \times 314 \times \frac 8{10} \\ & = 400 - 360 \\ & = \boxed{40} \end{aligned}

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