Dividing feet into inches

J

Jstaheli

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Sep 12, 2022
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Hello.
Im having difficulty solving this equation for one of my exams.
There is a hallway that is 24 feet long. You have 5 lights to install. What is the measurement between each light?
24x12= 288
288/5=57.6
57.6/12=4.8
8/10=1.25
So I end up with 4.125.
4.125 is not the correct answer according to the instructor, and he insists on me finding the answer instead of helping me solve the equation.
Is this the correct way to solve this equation? Please provide some guidance.
Thank you
JStaheli
 
Jstaheli said:
Hello.
Im having difficulty solving this equation for one of my exams.
There is a hallway that is 24 feet long. You have 5 lights to install. What is the measurement between each light?
24x12= 288
288/5=57.6
57.6/12=4.8
8/10=1.25
So I end up with 4.125.
4.125 is not the correct answer according to the instructor, and he insists on me finding the answer instead of helping me solve the equation.
Is this the correct way to solve this equation? Please provide some guidance.
Thank you
JStaheli
Click to expand...
Suppose you have a 24 ft long stick and you make 5 cuts at equal distances to get shorter sticks. How many "shorter" sticks would you get? How long would be each stick? How answer to this question would help you to answer your op?
 
Subhotosh Khan said:
Suppose you have a 24 ft long stick and you make 5 cuts at equal distances to get shorter sticks. How many "shorter" sticks would you get? How long would be each stick? How answer to this question would help you to answer your op?
Click to expand...
Thank you for your response. Ive tried that with an actual tape measure. I still come out to 4’ 9” 1/2. The answer that is needed is in a decimal format. Is there an equation that i can use to solve this problem?
 
Jstaheli said:
Hello.
Im having difficulty solving this equation for one of my exams.
There is a hallway that is 24 feet long. You have 5 lights to install. What is the measurement between each light?
24x12= 288
288/5=57.6
57.6/12=4.8
8/10=1.25
So I end up with 4.125.
4.125 is not the correct answer according to the instructor, and he insists on me finding the answer instead of helping me solve the equation.
Is this the correct way to solve this equation? Please provide some guidance.
Thank you
JStaheli
Click to expand...
I would recommend sketching the situation, to get a sense of exactly what you want to calculate.

SK's suggestion is an important part of this. But in addition, nothing has actually been said about how the lights are to be spaced, and if you were a contractor, that sketch would be a good way to communicate with your customer to make sure you understand their wishes. Do they want the same space between each pair of lights? Do they want that same space between the first or last light and the end of the hallway, or something different? It's possible that your answer would be correct, if they wanted a smaller distance there.

But there's an additional issue. You need to label the meaning of each calculation you do. You found that the hallway is 288 inches, and 1/5 of that is 57.6 inches. When you divide that by 12, you are converting to 4.8 feet. But what does your 4.125 represent?
 
Dr.Peterson said:
I would recommend sketching the situation, to get a sense of exactly what you want to calculate.

SK's suggestion is an important part of this. But in addition, nothing has actually been said about how the lights are to be spaced, and if you were a contractor, that sketch would be a good way to communicate with your customer to make sure you understand their wishes. Do they want the same space between each pair of lights? Do they want that same space between the first or last light and the end of the hallway, or something different? It's possible that your answer would be correct, if they wanted a smaller distance there.

But there's an additional issue. You need to label the meaning of each calculation you do. You found that the hallway is 288 inches, and 1/5 of that is 57.6 inches. When you divide that by 12, you are converting to 4.8 feet. But what does your 4.125 represent?
Click to expand...
4.125 inches

Jstaheli said:
4.125 inches
Click to expand...
Sorry, that was wrong. It is 4.125 feet

Subhotosh Khan said:
Please respond to the following question first.
Click to expand...
I would get 5 sticks of 57 5/8 inches each.

Jstaheli said:
I would get 5 sticks of 57 5/8 inches each.
Click to expand...
When i reverse the equation, I am over by an 1/8 inch. I have to go back for the exam in an hour and im trying to get the equation to figure out the answer in decimal format.

I reworked it again. It should be 4 foot .562 inches. Or 57 9/16 inches

Jstaheli said:
I reworked it again. It should be 4 foot .562 inches. Or 57 9/16 inches
Click to expand...
Sorry 4 foot 8 inches and . 562 inches
 
8/10 < 1, so 8/10 ≠ 1.25, which is greater than 1

To me the problem can have more than 1 answer.

Example: Suppose you have 12ft to place 5 bulbs.

You can put a light at 0 ft, 3ft, 6ft, 9ft and at 12ft (what did you do the 12ft to get the spacing to be 3ft?)

Now some people might say why put a light bulb at the beginning and end of the room?
If you choose not to, then you can put the light bulbs at 2ft, 4ft, 6ft, 8ft and 10ft (what did you do the 12ft to get the spacing to be 2ft?)
 
Last edited:
The instructor has obviously never worked as a lighting designer! Without telling you how far to leave between each end and the first and last light, the question is not solvable.
If you leave the same distance at the ends as you leave between the lights, you then have six equal spaces in 24 feet, which is 4' each. (However, in real life that will not give you an even distribution of light along the hall, which is actually rather important for safety reasons.)
 
Jstaheli said:
I would get 5 sticks of 57 5/8 inches each.
Click to expand...
Incorrect!

If you make 5 cuts, you would get 6 shorter sticks - of 4 ft. each.

Think about it -
if you make 1 cut you'll get 2 sticks.​
if you make 2 cuts you'll get 3 sticks. And so on .....​
 
Neither the required distance between the lights is given, nor a condition that the lights need to be in a straight line.
 
Alan Gilbert said:
The instructor has obviously never worked as a lighting designer! Without telling you how far to leave between each end and the first and last light, the question is not solvable.
If you leave the same distance at the ends as you leave between the lights, you then have six equal spaces in 24 feet, which is 4' each. (However, in real life that will not give you an even distribution of light along the hall, which is actually rather important for safety reasons.)
Click to expand...
Yes, this is why I said that the idea of dividing by 5 might be correct; it would be reasonable to have half as much space at each end as between two lights.

Jstaheli said:
4.125 inches

Sorry, that was wrong. It is 4.125 feet
Click to expand...
No. Here is your work, with units inserted:
Jstaheli said:
24 ft x12 in/ft = 288 in
288 in/5 = 57.6 in
57.6 in/12 (in/ft) = 4.8 ft
8/10=1.25 NONSENSE
So I end up with 4 ft and .125 in???
Click to expand...
You're trying to convert 4.8 ft to feet and inches. The answer will not be just inches or just feet, as you did it.
 
Dr.Peterson said:
You're trying to convert 4.8 ft to feet and inches. The answer will not be just inches or just feet, as you did it.
Click to expand...
I had to sign off quickly, so I didn't finish what I intended to say.

You have 4.8 feet, and want to convert it, you say, to decimal form.

If that meant decimal feet, then you are finished (if your approach, dividing by 5, were considered right).

If it meant decimal inches, then you already had it when you said 57.6 inches.

If it meant feet and (decimal) inches, then you have to convert the 0.8 feet to inches; you don't do that by dividing 8 by 10, or 10 by 8 as you actually did. To convert 0.8 feet to inches, you multiply by 12 (ft/in): 0.8*12 = 9.6 inches. So your answer would be 4 feet, 9.6 inches.

And you can check that: 4 feet is 48 inches; add 9.6 inches, and you have 57.6 inches, as you'd found.

To repeat, labeling units, and keeping track of what each number you calculate means, is essential in a complicated calculation like this.


But also, it is likely that your instructor thinks that there should be 5 lights with 6 equal spaces, like this:

|----o----o----o----o----o----|​

In that case, you would divide by 6, and the work is very easy.

A real lighting designer, as in post #9, might well want each light to be centered in an equal length of the hallway, in which case the end segments would be half as long as the others, and dividing by 5 would be appropriate:

|---o------o------o------o------o---|​
 
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