June 15th, 2014, 09:14 PM  #1 
Member Joined: Jun 2014 From: pennsylvania Posts: 45 Thanks: 0  Help me understand this problem. Hello, I just wanted some help on how to answer this type of question, I don't understand what I have to do. The 37 1/2 & 2 2/3 is what I guessed. I also wanted to know how to solve this one because I was only able to get so far before not being sure what to do, and the answer that I was supposed to choose from, I was unable to extrapolate from the equation. The last step I got to before I did not know what to do further was 15ax1 divide by 5 Last edited by skipjack; June 16th, 2014 at 11:14 PM. 
June 15th, 2014, 09:46 PM  #2 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,656 Thanks: 2634 Math Focus: Mainly analysis and algebra 
For the first one, you have the scale correct, but not the height. The bridge is 44 feet long, and on the diagram it is 16.5 inches. So we have 16.5 inches represents 44 feet. So how many inches represent 1 foot? Well, if we divide by 44 we get $\frac{16.5}{44} = 2 \frac{2}{3}$ inches represent $\frac{44}{44} = 1$ foot. We can do a similar thing in reverse for the height. We have 1 foot is represented by $2 \frac{2}{3} = \frac{8}{3}$ inches. We want 10 feet, so let's multiply by 10. Then 10 feet are represented by $10 \cdot \frac{8}{3}$ inches. For the second one you have $$3ax = \frac{1}{5}$$ So $x$ is multiplied by something: what? To isolate the $x$, we therefore divide both sides of the equation by that something. Last edited by skipjack; June 16th, 2014 at 11:11 PM. 
June 15th, 2014, 11:03 PM  #3 
Member Joined: Jun 2014 From: pennsylvania Posts: 45 Thanks: 0 
Thanks again v8 for giving me the time. First off I'm glad I got the scale right. But redoing it just now, I'm not sure on something. When I divide 16.5 by 44, I get 0.304 and if I turn that into a fraction I don't think I can turn it into the 2 2/3. And the last part I understand now, it was 26 2/3. I just need to exactly understand how we get that 2 2/3 scale? I'm sorry if I'm not understanding your answer to the second problem I had, but if you can elaborate a bit more I would appreciate it even more Last edited by skipjack; June 16th, 2014 at 11:16 PM. 
June 16th, 2014, 08:47 PM  #4 
Member Joined: Jun 2014 From: pennsylvania Posts: 45 Thanks: 0 
Sorry about my past post, everything checks out and you helped me solve the scale type of problem I might encounter again. But I still want to understand the other question so if you could please explain it to me. Thank you. Last edited by skipjack; June 16th, 2014 at 11:16 PM. 
June 16th, 2014, 11:52 PM  #5 
Global Moderator Joined: Dec 2006 Posts: 20,632 Thanks: 2080 
There are mistakes in the above. As 16.5 in. represents 44ft, 3/8 in. represents 1 ft, and so 3 3/4 in. represents 10 ft. Thus 3 3/4 should have been dragged to the height box and 3/8 should have been dragged to the Scale box. To solve 3ax = 1/5, divide both sides by 3a. That gives x = 1/(15a), which is choice A. 
June 17th, 2014, 04:58 AM  #6 
Math Team Joined: Dec 2013 From: Colombia Posts: 7,656 Thanks: 2634 Math Focus: Mainly analysis and algebra 
There are plenty of mistakes in my first post. I apologise. I'll look at it again later.

June 17th, 2014, 08:43 AM  #7 
Member Joined: Jun 2014 From: pennsylvania Posts: 45 Thanks: 0 
Thanks skipjack for the correction. I want to make sure I get this 100%. Ok, I really wanna figure this out. I guess I was trying to solve it differently? I got stuck on 15ax1 divide by 5 If I do it the way you mention, can you please show me how I divide 3a into 1/5. If I divide 3a into 3ax, am I not left with 1x? I'm not sure how to divide the 3a into the 1/5. Can you guys please explain the first problem to me? I'm not getting 3/8 in my calculations. When I was explained, it was 2 2/3; I was able to get that calculation. So please tell me what needs to be corrected, and what to do so I can understand. Thanks Last edited by skipjack; June 18th, 2014 at 12:01 PM. 
June 18th, 2014, 12:13 AM  #8 
Member Joined: Jun 2014 From: pennsylvania Posts: 45 Thanks: 0 
~bump

June 18th, 2014, 02:40 AM  #9 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 14,414 Thanks: 1024 
RULE: (a/b) / (c/d) = (a/b) * (d/c) = (ad) / (bc) : you knew that, right? (1/5) / (3a/1) = (1/5) * (1/(3a)) = 1 / (15a) .... slap your forehead !! 
June 18th, 2014, 12:21 PM  #10 
Global Moderator Joined: Dec 2006 Posts: 20,632 Thanks: 2080 
In the first problem, 16.5in. represents 44ft, so (16.5/44)in. represents 1ft. To evaluate 16.5/44, I first doubled the numerator and denominator to get 33/88, then I divided the numerator and denominator by 11 to get 3/8. Thus (3/8)in. represents 1ft, and so (30/8)in. represents 10ft. As 30/8 = 3 3/4, that means (3 3/4)in. represents 10ft. In the second problem, dividing 3ax by 3a gives x. Dividing 1/5 by 3a is done by multiplying 1/5 by 1/(3a). $$\frac15 / (3a) = \frac15 \times \frac{1}{3a} = \frac{1 \times 1}{5 \times 3a} = \frac{1}{15a}$$ 

Tags 
problem, understand 
Search tags for this page 
3ax=1/5,3ax=1/5 solve for x,3ax = 1/5,solve the equation for x 3ax=1/5,3ax = 1/5 solve for x,solve 3ax=1/5,3ax= 1/5 answer,what is 3ax = 1/5,solve for x 3ax=1/5,Solve the equation for 3ax =1/5,1/5 divided by 3a,what's the scale for 44 feet to 16.5 inches,scale is 16.5inches real is 44feet,a bridge is 44 ft long. the model is 16.5 inches. what is the scale,44 feet to 16.5 inches
Click on a term to search for related topics.

Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Couldn't understand this problem..  pnf123  Calculus  0  April 4th, 2014 10:02 PM 
need help to understand  ment0smintz  Calculus  6  February 18th, 2013 12:07 PM 
Help me understand this?  goodjobbro  Number Theory  13  December 25th, 2012 06:36 PM 
I don't understand this...  johnny  Algebra  1  July 21st, 2009 01:18 AM 
can someone help me understand this  Williamson  Calculus  5  July 13th, 2008 09:17 AM 