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# Thread: i need help first year math!

1. Junior Member
Join Date
Feb 2008
Posts
1

## i need help first year math!

Eh, my name is Trisha and i have become a welder. I have no problem with the hands on work. i am currently going to school as a first year apprentice.My question for you is if anyone out their can help me with some math right now i am doing ratios and i don't under stand how to take to ratios and make them into one

example:

a journeyman welder can weld 120 lengths of pipe per 40-hour week while his apprentice can weld one pipe every half hour. what is the ratio of the journeyman's rate of work to the apprentice's rate of work?

another example:

on a shop drawing, the length of a pipe is 2 3/4''. the actual length of the pipe is 12'-6''long what is the ratio of the blue print length to the actual length?

i know how ratios work i'm just having a hard time to figur out the correct method used for this problem

this may be too late to be asking all you people considering i will be tested this week so if anyone out their may be able you help me out please add me im smokey_spunk@hotmail.com

2. hey trisha welcome to the site. Theres many people here who are very knowledgable and skilled at what they do here and there is much to learn. Now for the first example you have to find out how many lengths of pipe the journeyman can weld per half hour and to find that out you use a formula.

120 lengths y
----------- = ---
40 hours .5 hours

then you cross multiply to get 40y=120x .5 and then you get 40y=60.. so you take 60/40 to get y or your unknown and that ends up being 1.5 lengths per 1/2 hour... do the journeymans ratio to the apprentaces would be 1.5:1

im pretty sure this is right but if im wrong im sure there is someone who will correct me.
Good luck on your test and welcome to the site

3. Reduction of fractions is all you have to do...ie convert the app. can weld 80 per 40 hrs...so the ratio is 80:120......reduce that to 2:3 is the lowest you can reduce it...so for every 2 from the app. the journy will turn out 3....so to answer the question of journy to app. it would be 3:2....good luck and welcome aboard...

EDIT:
I stand corrected you have to go to 1 so yes 3:2 would reduce to 1.5:1......

4. Senior Member
Join Date
Dec 2007
Location
alabama
Posts
759
thats what i got figured.to help understand this ; the apprentice can weld two per hour,thats 80 on a 40 hour work week ,the journeyman can do 120 on a 40 hour work week.divide 80 into 120 and you get 1.5 to 1. now by looking at these numbers i would have to say they are non-union
on the other problem on finding the scale of a drawing,i divided 2 3/4 into 12-6 and came up with 54.5 unless my thinking was wrong the scale would be 54.5 to 1. any other ones out there feel that this is right?

5. fabricator , yep your math checks out .
Trish , math can be a headache at times , but math is something you will use everyday out on the job so learn it well . When I entered my apprenticeship I had been out of school for 19 years . I am a journeyman steamfitter now . Dan

6. Senior Member
Join Date
Dec 2007
Posts
157

## Homework

Always start by checking to make sure you are using the same unit of measure: inches vs feet, ounces vs pounds, mm vs cm vs m, etc.

In your second problem the ratio is simply 2.75 inches to 12.5 feet. For every 2.75 inches drawn, you have a 12.5 feet (12' 6") of actual structure. That is a ratio or in this case the "scale" to which it is built.

The rest of the proceedure is just converting to like units of measure 12.5 feet equal 150 inches. So... 2.75" to 150".

and then reducing...

2.75 over 150 reduces is 1:54.55 For every 1" there is 54.6" of structure, for 2.75" there is 150" of structure.

In real life an architect would use a typical scale of 1/8", 1/4" or 1/2" to (equals) 1 foot.

1/4" scale example: 2.75" = 11/4 or 11 feet

An engineer, more likely for a mechanical or shop drawning may use a mechanical scale which divides the inch into various units of a base ten sytem. Simply, divides an inch into 10, 20, etc segments. This seem confusing, but it better correlates to decimal measurements vs fractions which actually makes the math easier.

It is very important to spend the time and get a good grasp of scaling and reading drawings. I am a general contractor and let me tell you that what seperates the pros from the others down the road is their layout abilities and ability to read and understand drawings and turn them into reality. It may be much more boring that making sparks of cutting wood but it is critical.

Best of luck,

John

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