A community for students.
Here's the question you clicked on:
 0 viewing
anonymous
 3 years ago
Help in b) iii) only thanks :D
anonymous
 3 years ago
Help in b) iii) only thanks :D

This Question is Closed

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0@nbouscal @satellite73 @TuringTest

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0@jim_thompson5910 @dpaInc @KingGeorge @AccessDenied @SmoothMath

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1I'm pretty sure I have the answer, but I'm not sure yet. What lengths did you get for KM and KN?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0for KM i got 27 and KN i got 15

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Give me a minute to see if I was correct.

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1So I have the answer, but I don't think I did it a very good way. Basically, I found the area of KLM using herons formula and the area of LNM using heron's formula. You also know using some alternating angles of the parallel lines, that triangle LNM is twice the area of triangle NPM, so that let's you find the area of NPM, and then you subtract that off from the area of KLM to find the area of the trapezium KLPN

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0what iis herons formula? can u show the woking?

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Heron's formula is a way to find the area of any triangle if you know the side lengths. If you want the general formula, look here: http://en.wikipedia.org/wiki/Heron's_formula Otherwise, I'll just skip the more tedious work and show you how I got the solution.

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1(I'm skipping the simplification here, but you should check it on your own) Using that, we get that the area of KLM is \[90\sqrt{2}\]and the area of LNM is \[40\sqrt2\]

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Thus, the area of NPM is \[\frac{40\sqrt2}{2}=20\sqrt2\]Now, we just put all these numbers in the ratio \[\frac{20\sqrt2}{90\sqrt220\sqrt2}=\frac{\sqrt2}{\sqrt2}\cdot\frac{20}{70}=\frac{2}{7}\]And there's the solution.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0but the solution actually is 16/65...according to the markin gsolution...hmm

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1It might be a typo since \[\frac{2}{7}=\frac{16}{56}\]So the two possibilities are that there's a typo, or your lengths for KM and KN were incorrect.

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Could you briefly explain to me how you got the length of KN?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0i used similarity triangle method...like il show the working...first i found KM LK/LN=KM/LM 15/10=KM/18 KM=27 then i found NM= LK/LM=LM/NM 15/10=18/NM NM=12 then KN= KMNM 2712= 15cm :)

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Definitely no mistakes there. That means that I'm pretty sure it's a typo in the book.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0just check if ur answer is wrong, coz it has to be 16/65

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0okay can u help in another one..its algebra?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0\[\frac{x^{2}}{5} + \frac{5}{x} = \frac{1}{2}x +3\] can u equal them so that one side will have 0

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Sure, give me a few more seconds to finish checking my first solution. I came up with another, far easier way to find the ration.

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1I might have found a better solution... It's not working out as well as I had anticipated. As for the algebra question, multiply everything by \(x\). You'll get a cubic where you can easily move everything to one side, and hopefully be able to factor.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0can u do it, im stuggling like showing a working

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1It might even be better to multiply the thing by 10x to get rid of the 5 and the 2 in the denominators as well. That would get you \[2x^3+50=5x^2+30x\]Move everything to one side, \[2x^35x^230x+50=0\]

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Unfortunately, that doesn't seem to be factoring very easily. And you were right to call me out on my previous solution to the triangle question. I don't think I'm right.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0well how did u get 2x^3 + 50?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0any other methods? to do that algebra?

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1\[x(\frac{x^{2}}{5} + \frac{5}{x}) = x(\frac{1}{2}x +3)\]Distribute the x\[(\frac{x^{3}}{5} + 5) = (\frac{1}{2}x^2 +3x)\]Now mulitply everything by 10 to get \[(\frac{10x^{3}}{5} + 50) = (\frac{10x^2}{2} +30x)\]Simplify things, \[2x^3 + 50 = 5x^2 +30x\]and move everything to one side.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0any other easy method, because i can remembr once i did it in an easy way?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0it is just 1 mark question?

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1I'm not sure I understand. Do you just want to set one side equal to 0 and solve for x on the other side?

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1I'm still here. So if we set one side equal to 0, we want to find solutions to the equations \[\frac{x^2}{5}+\frac{5}{x}=0\]and \[0=\frac{x}{2}+3\] correct?

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0no i mean, both the equations should be simplified and be equal = 0

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Can we come back to that in a minute, I just figured out the easy way to do the triangle problem, and the book's correct. (It really shouldn't have taken me this long).

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Since NP is parallel to KL, you can show that triangle NPM is similar to triangle KLM. You know that angle K is the same as angle MNP, by corresponding angles. Also, for the same reason, angle KLM is the same as angle NPM, so this means that the triangles are similar. Now let the area of triangle NPM=A. The ratio between the sidelengths of NPM and KLM is exactly 9/4. Since the formula for area of a triangle is 1/2 bh the area vary as a square, so we square it to get that the area of KLM=81/16 A.

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1The area of the trapezium is the area of KLM minus the area of NPM. So that area is given by \[\frac{81A}{16}A=\frac{65A}{16}\]Now we take A over that, and we get \[\frac{A}{\frac{65A}{16}}=\frac{16A}{65A}=\frac{16}{65}\]is the ratio.

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0how did u get 65/16 in the first place

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1\[\frac{81A}{16}A=\frac{81A}{16}\frac{16A}{16}=\frac{81A16A}{16}=\frac{A(8116)}{16}=\frac{65A}{16}\]

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1And I got the 81/16 because the ratio of the side lengths is 9/4, and the ratio of the areas (of the triangles) is the ration of the side lengths squared. So \[\left(\frac{9}{4}\right)^2=\frac{81}{16}\]

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1\[\frac{27}{12}=\frac{9}{4}\]I just simplified the ratio between KM and NM

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0oh okay thats the point..

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1Yup. I should have seen that earlier :(

anonymous
 3 years ago
Best ResponseYou've already chosen the best response.0alright thanks alot man, for ur time...ur a great teacher :)

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1thanks for the compliment :)

KingGeorge
 3 years ago
Best ResponseYou've already chosen the best response.1I've got to go, so if you still need help with the algebra question, just post it in another question, and hopefully some one will answer it. Good luck!
Ask your own question
Sign UpFind more explanations on OpenStudy
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.