3 Squares inside triangles

Geometry Level 3

The numbers inside the squares shows the area of the corresponding square, if A C A B = a 8 b \dfrac{\overline{AC}}{\overline{AB}}=\dfrac{\sqrt{a}}{8\sqrt{b}} where a a and b b are square free natural numbers then find a + b a+b


The answer is 234.

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2 solutions

Dwaipayan Shikari
Mar 13, 2021

I n A B C O A O C = A M B M A C O C = A B M B A C A B = O C M B {In}\:\bigtriangleup{ABC}\:\:\:\frac{{OA}}{{OC}}=\frac{{AM}}{{BM}}\:\:\:\Rightarrow\frac{{AC}}{{OC}}=\frac{{AB}}{{MB}}\Rightarrow\frac{{AC}}{{AB}}=\frac{{OC}}{{MB}}

I n L H C ( l a r g e h a d r o n C o l l i d e r ! : ) a n d O L X 4 {In}\:\bigtriangleup{LHC}\:\left({large}\:{hadron}\:{Collider}\:!:\right){and}\:\bigtriangleup{OLX}_{\mathrm{4}} S i n c e L H C O L X 4 {Since}\:\bigtriangleup{LHC}\sim\bigtriangleup{OLX}_{\mathrm{4}}

L H C H = O X 4 X 4 L 5 H C = 13 5 5 H C = 25 8 \frac{{LH}}{{CH}}=\frac{{OX}_{\mathrm{4}} }{{X}_{\mathrm{4}} {L}}\:\Rightarrow\frac{\mathrm{5}}{{HC}}=\frac{\mathrm{13}-\mathrm{5}}{\mathrm{5}}\Rightarrow{HC}=\frac{\mathrm{25}}{\mathrm{8}}

Similarly in G J B a n d M X 4 G , M X 3 G X 3 = G J J B 13 12 12 = 12 B J \bigtriangleup{GJB}\:{and}\:{MX}_{\mathrm{4}} {G}\:,\frac{{MX}_{\mathrm{3}} }{{GX}_{\mathrm{3}} }=\frac{{GJ}} {{JB}}\Rightarrow\frac{\mathrm{13}-\mathrm{12}}{\mathrm{12}}=\frac{\mathrm{12}}{{BJ}} B J = 144 \implies{BJ}=\mathrm{144}

O C = O L + L C = ( 13 5 ) 2 + 5 2 + 25 2 64 + 25 = 13 89 8 {OC}={OL}+{LC}=\sqrt{\left(\mathrm{13}-\mathrm{5}\right)^{\mathrm{2}} +\mathrm{5}^{\mathrm{2}} }+\sqrt{\frac{\mathrm{25}^{\mathrm{2}} }{\mathrm{64}}+\mathrm{25}}=\frac{\mathrm{13}\sqrt{\mathrm{89}}}{\mathrm{8}}

B M = G M + B M = 12 2 + 1 2 + 12 2 + 12 4 = 13 145 {BM}={GM}+{BM}=\sqrt{\mathrm{12}^{\mathrm{2}} +\mathrm{1}^{\mathrm{2}} }+\sqrt{\mathrm{12}^{\mathrm{2}} +\mathrm{12}^{\mathrm{4}} }=\mathrm{13}\sqrt{\mathrm{145}}

A C A B = O C M B = 89 8 145 \frac{{AC}}{{AB}}=\frac{{OC}}{{MB}}=\frac{\sqrt{\mathrm{89}}}{\mathrm{8}\sqrt{\mathrm{145}}}

So answer is 89 + 145 = 234 \boxed{89+145}=234

Saya Suka
Mar 15, 2021

Since the quest is to find a ratio, we can ignore the real triangular side lengths and just use a similar ones. CA's side inclination is √25 = 5 units to the right and √169 - √25 = 13 - 5 = 8 units up, for a slope of 8/5, while AB's side inclination is √144 = 12 units to the right and √169 - √144 = 13 - 12 = 1 units down, for a slope of -1/12 = -8/96 just to make the nominators, or the equal heights, a match. The ratio is equal to √(8² + 5²) : √(8² + 96²) = √(8² + 5²) : 8√(1² + 12²) = √(64 + 25) : 8√(1 + 144) = √89 : 8√145.

Answer
= 89 + 145
= 234

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