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#1 2021-06-30 09:38:55

Nickm62388
Member
Registered: 2021-06-30
Posts: 2

Cannot find formula or solution to get answer for feet/inch addition

I have the answer to these two problems, but cannot figure out how they were got, and cannot find a formula or anything online to get the answer please help


Problem #1

   17ft. 7 1/2in.
-  14ft. 9 7/8in.

=??????????

Problem #2

   59degrees 37’ 18”
-   40 degrees 43’ 22”

=????? I don’t understand how you subtract something with degrees and feet and inches

Again I have the answers from the answer key but no idea how the answers came to be…

Please help

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#2 2021-06-30 12:04:59

ganesh
Administrator
Registered: 2005-06-28
Posts: 34,320

Re: Cannot find formula or solution to get answer for feet/inch addition

Hi Nickm62388,

Welcome to the forum!

Please see the links:

US Standard Lengths.

Degrees (Angles).

Minute (angles).

Second (angles).


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#3 2021-06-30 12:23:39

Nickm62388
Member
Registered: 2021-06-30
Posts: 2

Re: Cannot find formula or solution to get answer for feet/inch addition

I appreciate the links, but with the equations I listed. I don’t see how exactly they relate or help answer them with the links. hmm//

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#4 2021-06-30 17:29:19

phrontister
Real Member
From: The Land of Tomorrow
Registered: 2009-07-12
Posts: 4,695

Re: Cannot find formula or solution to get answer for feet/inch addition

Hi Nickm62388;

Here's my way of tackling these (others may have different methods).

Problem #1
The inches & fraction components in the first length are less than their counterparts in the second length, which adds difficulty to subtracting imperial lengths, particularly those with fractions.

To make the subtraction easier, I start with the following three steps:
1. convert the fraction to the Least Common Denominator (LCD); then
2. adjust the value of the fraction component to make it greater than that of the second length; then
3. adjust the value of the inches component to make it greater than that of the second length.

That leaves a simple subtraction exercise.

Btw, the 'take' and 'add' terminology that I used is like 'borrow' and 'pay', now aka 'regrouping', and is how I've always understood that concept.

Also, I've used symbols ' and " instead of abbreviations 'ft' and 'in' respectively...a common notation practice for these imperial length units.

RFl2IWO.jpg

Formula: You could convert both lengths to eighths of an inch, deduct the second from the first, and convert the result to feet, inches and eighths:

That last conversion from eighths is a bit tricky...

Problem #2
Same approach as for Problem #1:

1ifjGt0.jpg

Formula: You could convert both angles to seconds, deduct the second from the first, and convert the result to degrees, minutes & seconds:

Last edited by phrontister (2021-09-10 11:33:29)


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