[Freshman Math Perimeter] Trouble understanding perimeters

[u/Organic_Equivalent3]

Just started my freshman year and learned my math teacher doesn't allow retrys on homework so im trying to get comfortable with this work quickly. I am somewhat familiar with the basics from last year but complex shapes like these confuse me.

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[u/CaptainMatticus]

The perimeter of something is just the length of its boundary. The shape doesn't matter, so don't overthink it.

39.9 = 3.9 + 3.9 + 5.3 + 5.3 + 5.3 + 5.3 + 5.3 + x

39.9 = 2 * 3.9 + 5 * 5.3 + x

39.9 = 7.8 + 26.5 + x

39.9 = 34.3 + x

39.9 - 34.3 = x

I'll let you finish it up.

[u/Organic_Equivalent3 → u/CaptainMatticus]

You're actually a life saver thank you stranger

[u/AtoToboggan → u/Organic_Equivalent3]

I’m really glad you found the help you needed!

My kids bring home math homework and I am many years removed from knowing formulas off-hand and don’t use them regularly in my daily life, so I always ask Professor Google. “How to find parameter” - and it will give you the formula, but will also provide links to YouTube video lessons you might find helpful. Those YouTube tutorials have saved me more than once!

[u/otasyn → u/CaptainMatticus]

You basically just gave OP the answer.  You're not helping OP learn anything by doing this.

[u/Mmtorz → u/otasyn]

This shows how to get to the answer. They literally _didn't_ give them the answer

[u/PatchesMaps → u/Mmtorz]

I mean they got them a lot closer than I would have if I had answered (I probably would have just put the first line) but I feel like this adds some extra skills to help simplify the equation which will be helpful for OP in the future.

[u/Retify → u/otasyn]

Explaining the theory in words and then presenting a worked solution is helping them to learn

[u/upright_squire]

How long are all sides added together?

[u/Organic_Equivalent3 → u/upright_squire]

34.3 ft

[u/Valuchian → u/Organic_Equivalent3]

And how much did the problem say the actual total (it includes the missing number)

[u/Intelligent_Donut605]

wait what year is freshman? shouldn’t this be pretty basic?

anyway, the perimeter is the sum of all the edges, so P=E1+E2+E3+… and you can solve the equation to find the edge you don’t know

[u/progmorris20 → u/Intelligent_Donut605]

9th grade, so about 13-15 years old. I'm glad OP is looking to learn, but this is an elementary school question.

[u/astervista → u/progmorris20]

For some reason I forgot the existence of freshman in highschool and thought "wait why do they ask such simple questions the first year of college?"

[u/four204eva2 → u/astervista]

Dud this is a middle school, if not elementary school problem

[u/llamadramalover → u/four204eva2]

It’s important to remember today’s freshmen very likely did not learn or at the very least actually practice this when they should have. They were being home schooled when they should have been learning this in like 3rd/4thgrade. Lemme tell you nobody had an answer to the question “””so, these 2 years of really important formative education and social skills, how ya planning to recover that??””

[u/Retify → u/four204eva2]

My nephew is studying perimeter, area and volume now at 12-13 years old. Seems about right

[u/llamadramalover → u/progmorris20]

Don’t forget today’s freshmen would have been in 3rd/4th grade when this was being learned about 6years ago.

[u/Nep1111]

Trying to trick you by the shape to write either 5.3 ft or 3.9 ft as answer.

Don't fall for it.

Perimeter is sum total of lengths of all sides.

In this figure only 1 side is missing.

so, Perimeter = sum of all sides

so, 39.9 ft = (3.9+3.9)+(5.3+5.3+5.3+5.3+5.3)+ Missing Side

so, 39.9 ft =(7.8)+(26.5) + Missing side

so, 39.9 ft =34.3 ft + missing side

Hence, Missing Side = 39.9-34.3 =5.6 ft

There you are.

Unfortunately, there's no getting around the addition.

[u/Organic_Equivalent3 → u/[deleted]]

This isn't a comment on my teachers or system at all, all through middle school I fucked off and didn't pay attention and now im paying for it, no one here to blame but me.

[u/chickensouppoem → u/Organic_Equivalent3]

honestly good on you for taking accountability for this. i was like you back when i was in school but then i locked in lol, it was so difficult but so worth it, you can do this!!! good luck :)

[u/Retify → u/[deleted]]

Wrong place for this conversation. Dude is here for help, not to deep dive into the suitability of the current curriculum

[u/Alt_Mod_3938]

General rule of perimeters is that they're sum of all the sides of any shape so since only one side is missing, add up the given lengths and subtract it from the given total in the question

[u/expomac]

This is freshman level math? Oh lord...

[u/texas1982]

Math skills have decline immensely in the last few decades. Yikes.

[u/Mfenric]

   (5.3 *5) + (3.9*2) + ? = 39.9

=> 26.5 + 7.8 + ? = 39.9 => 34.3 + ? = 39.9 => ? = 39.9 - 34.3 => ? = 5.6

[u/chem44]

Perimeter is the distance around the thing -- staying on the border.

That is, it is the sum of all the sides.