Real Life Usage of GCF and LCM - ProTeacher Community
 Join the conversation! Post now as a guest or become a member today.

##### Real Life Usage of GCF and LCM

>

 Beagles Joined: Jun 2008 Posts: 1,264 Senior Member
Beagles

Joined: Jun 2008
Posts: 1,264
Senior Member
Real Life Usage of GCF and LCM
09-23-2009, 03:12 PM
 #1

I posted this on the Math board, but since I teach fifth grade, I hope my fifth grade colleagues will help me!

What is the real life usage of knowing GCF and LCM? I need it soon!
Thanks

 parker Joined: Mar 2006 Posts: 1,513 Senior Member
parker

Joined: Mar 2006
Posts: 1,513
Senior Member
Funny
09-23-2009, 05:18 PM
 #2

I was just googling problems for this. This is what I found.

When do I use LCM and when do I use GCF?
GCF
Do we want to split things into smaller sections?
Are we trying to figure out how many people we can invite?
Are we trying to arrange something in rows or groups?
LCM
Do we have an event that will be repeating over and over?
Will we have to purchase or get multiple items in order to have enough?
Are we trying to figure out when something will happen again at the same time?

ex.
Shannon is making identical balloon arrangements for a party. She has 32 maroon balloons, 24 white balloons, and 16 orange balloons. She wants each arrangement to have the same number of each color. What is the greatestnumber of arrangements that she can make if every balloon is used?

Bridget has swimming lessons every fifth day and diving lessons every third day. If she had a swimming lesson and a diving lesson on May 5, when will be the next date on which she has both swimming and diving lessons?

Boxes that are 12 inches tall are being stacked next to boxes that are 18 inches tall. What is the shortest height at which the two stacks will be the same height?

You are making pumpkin pies for the bake sale. Piecrusts are sold in packages of 3. Pie filling is sold in 4-can packages. What is the least number of piecrusts and filling that you can buy to have the same number of each?
How many of packages of each should you buy?

 Beagles Joined: Jun 2008 Posts: 1,264 Senior Member
Beagles

Joined: Jun 2008
Posts: 1,264
Senior Member

09-23-2009, 06:11 PM
 #3

This is great, thank you. I wanted something but couldn't find anything. Must have not Googled right. Thanks!!

 chad17 Joined: Jul 2007 Posts: 229 Full Member

Joined: Jul 2007
Posts: 229
Full Member
Hot dogs
09-25-2009, 03:38 PM
 #4

Hot dogs and buns are an example I always use. Hotdogs come in packages of 10, while rolls come in either 8 or 12. What's the smallest number of each you have to buy to have the same number of each?

 Kat1019 Joined: May 2008 Posts: 41 Junior Member
Kat1019

Joined: May 2008
Posts: 41
Junior Member
Hot dogs
10-03-2009, 06:45 PM
 #5

That hot dog bun is a perfect example of real-life application! Thanks for sharing!

 Liese Guest
Liese

Guest
Thank you parker!
11-22-2009, 07:39 AM
 #6

This helped a TON! Like, you have no idea!

 sportwinds Joined: Jul 2008 Posts: 145 Full Member
sportwinds

Joined: Jul 2008
Posts: 145
Full Member
application of GCF
11-25-2009, 05:40 AM
 #7

I present GCF as a tool for simplifying fractions. So, any real life use of fractions, will be a real life application of GCF.

 Appreciative Guest
Appreciative

Guest
Guest
02-04-2010, 06:27 AM
 #8

Thank you very much for this example! It really helped. I have used planets' orbits for LCM as well. I also use an example of three friends wanting to spend their next day off of work together for LCM. One friend works 5 days with one day off, the next 6 days with one day off, and the last 7 days with one day off. If they just enjoyed a day off together, how many days until the time when they can enjoy a communal day off?

 Anonymous T Guest
Anonymous T

Guest
Another use
02-16-2010, 10:29 PM
 #9

Students find GCF all the time when reducing fractions. Anything that requires you to reduce a fraction or a ratio requires finding GCF.

 Pouli Guest
Pouli

Guest

11-12-2010, 09:47 PM
 #10

Very good for daily life example! Very helpful

 MathAPhobic Guest
MathAPhobic

Guest

01-08-2013, 03:18 AM
 #11

Thank you SO much, this really helped me!

 nihcorb Joined: Jun 2010 Posts: 1 New Member
nihcorb

Joined: Jun 2010
Posts: 1
New Member
Hot Dogs and Buns
06-12-2013, 07:14 AM
 #12

Search "Father of the Bride" on YouTube. There is a short section where he freaks out because he can't buy equal packs of hot dogs and buns...great hook for kids!

 CaptMorgan72 Guest
CaptMorgan72

Guest
I don't understand
02-11-2014, 03:37 PM
 #13

I see the hot dog/bun example for explaining real world use of the lcm but I don't understand it. I used prime factorization for 10,8 and end up with lcm = 2x5x2x2 = 40. So 40 is the lcm of 10 and 8. Now if I buy 40 packs of hot dogs that is 400 hot dogs and 40 packs of buns is 320 buns. I am 80 buns shy for my 400 dogs. I don't understand.

 Captmorgan72 Guest
Captmorgan72

Guest
I understand now
02-12-2014, 02:57 AM
 #14

I did some research and now I understand.

 whoswho Guest
whoswho

Guest
thank you for clarifying your confusion!
03-06-2014, 07:27 AM
 #15

I would have missed the principle behind it if you hadn't stated the 400 issue. It's not 400 hotdogs and 400 buns. It's 40 hot dogs and 40 buns. 40/8=5 & 40/10=4. Therefore, it's five packs of hot dogs and four packs of buns.

 AugustRose Guest
AugustRose

Guest
LCM real life situations
08-21-2014, 08:32 PM
 #16

i do this problem every year, but the "father of the bride" hot dog buns clip really helps engagement.

another good one is something like ...
KSHE radio plays top hits all weekend. They have been playing the new song by "RUcool" every 18 minutes. KDHX has been playing the new song every 24 minutes. If they both play the song at 3:00 PM, when will the next time be that they play the song at the same time?

 Billy obit Guest
Billy obit

Guest

11-06-2014, 10:13 AM
 #17

That's a good example with the hot dog buns thx a lot

 anita burke Guest
anita burke

Guest
amateur tutor
11-24-2015, 11:33 AM
 #18

Just do what Steve Martin did in Parenthood and tear open the bun packages

 Cmoreofme Guest
Cmoreofme

Guest
I do not understand why?
01-29-2016, 06:09 AM
 #19

I do not know but is this correct? Here I found some problems: I see the hot dog/bun example for explaining real world use of the lcm but I don't understand it. I used prime factorization for 10,8 and end up with lcm = 2x5x2x2 = 40. So 40 is the lcm of 10 and 8. Now if I buy 40 packs of hot dogs that is 400 hot dogs and 40 packs of buns is 320 buns. I am 80 buns shy for my 400 dogs. I don't understand.

 anoynymus Guest
anoynymus

Guest

03-18-2016, 03:22 AM
 #20

are there any other real life examples?

 No one Guest
No one

Guest

06-23-2016, 05:51 AM
 #21

40 is the number where the hotdog and the buns meet. So basically it means that u need to buy x number of hotdogs which is 4 and y number of buns which is 5. So the ans is 4 packs of hotdogs and 5 packs of buns.

 Scuders Guest
Scuders

Guest

08-22-2016, 09:39 AM
 #22

They're all (great) examples of LCM. I can't for the life of me think of real world application for HCF/GCF!! (Simplifying fractions is not real world and kids quickly spot it's quicker to divide by 2 then 2 then 3 than calculate that the HCF is 12 and then divide.)

Join the conversation! Post as a guest or become a member today. New members welcome!

>