The image shows a portion of a bridge supported by vertical pillars from the slope below. What is the length of the bridge between pillar B and pillar C?

- anonymous

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- anonymous

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- anonymous

Use pythagoras theorem for this question, both of em are similar triangles

- anonymous

I honestly do not know how to.

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## More answers

- anonymous

i cant really help you the image is really fuzzy

- anonymous

and i dont run csi enhancer

- anonymous

do you know how to do the process you were talking about ? could you explain to me how to ?

- anonymous

ok lets start by finding this angle|dw:1438434416019:dw|

- anonymous

29 feet
48 feet
56 feet
60 feet
those are my options btw. And alright.

- anonymous

\[\cos^{-1} (\frac{ 40 }{ 50 }) is the \angle\]

- anonymous

cos^1 (40/50) is the angle

- anonymous

im really confused.

- anonymous

|dw:1438434482105:dw|

- anonymous

okay from a to b on the top is 40 feet, bottom is 50 feet. and b to c on bottom is 70 feet,
does that help ?

- anonymous

\[\frac{ 50 }{ 120 } = \frac{ 40 }{ 40+x }\]

- anonymous

now you can solve for x

- anonymous

you can do that i hope

- anonymous

i got 80 .. i feel like im wrong ... I havent had a math class since my freshman year in high school, and this is my senior year, and i just honestly dont have any idea what im doing ... i feel really stupid right now.

- anonymous

lemme try solving\[\frac{ 50 }{ 120 } = \frac{ 40 }{ 40+x }\]\[50 = \frac{ 4800 }{ 40+x }\]\[50(40+x)=4800\]\[2000+50x=4800\]\[50x=2800\]\[x=56\]

- anonymous

thank you ...
But can i ask how you did that process ? if its too much to explain thats fine.

- anonymous

alright you just cross multiple the denominator to each sides to cancel them out (the 1st 2 lines).

- anonymous

cause fractions are messy. then you move the constant to one side of the equation (3rd line), by minus-ing the constant (2000) from both sides.

- anonymous

thats how we end up with 50x=2800

- anonymous

This whole thing confuses me. I literally feel dumb. I don't understand any of this.

- anonymous

which part you do not understand?

- anonymous

All of it... I don't even have a teacher, like i have to teach myself all of this stuff. Im probably wasting your time honestly, I cant comprehend this kind of stuff.

- anonymous

ok ill write it in simpler form

- anonymous

You don't have to do that..

- anonymous

you gotta know how we come out with that first....

- anonymous

otherwise you will keep getting stuck

- anonymous

I just dont want to waste your time. And i don't think ill ever understand this.

- anonymous

well just take it easy, 1 thing at a time

- anonymous

okay..

- anonymous

ill explain to you how the\[\frac{ 50 }{ 120 } = \frac{ 40 }{ 40+x }\] is made first

- anonymous

the triangle in the diagram is a similar triangle, therefore they are proportional to each other|dw:1438436528358:dw|

- anonymous

okay

- anonymous

50+70 is how we got the 120., and we take the ratio of the smaller triangle to the larger one

- anonymous

ratio ?

- anonymous

yea the fraction you saw 50/120 is the ratio

- anonymous

okay.

- anonymous

now the other side of the triangle is 40 on small side and 40+x on larger side

- anonymous

they have to be proportional because they are co-linear so the ratio (that fraction) must be equal

- anonymous

okay.

- anonymous

you can understand that?

- anonymous

i think.

- anonymous

lemme try draw something to show you what i mean|dw:1438437049240:dw|

- anonymous

okay

- anonymous

like this in case the ratio of the triangle is 1:2 or 1/2

- anonymous

its similar as the question you had but the proportion is not so straightforward

- anonymous

so we use the ratio to find the distance of 40+x, with the ratio of the 50/120

- anonymous

I have to go. Can we finish this later ?

- anonymous

sure and see ya!

- anonymous

okay , thank you. i gave you a medal.

- anonymous

thank you

- anonymous

no problem.

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