Real Life Usage of GCF and LCM - ProTeacher Community





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Real Life Usage of GCF and LCM
Old 09-23-2009, 03:12 PM
 
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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


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Funny
Old 09-23-2009, 05:18 PM
 
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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?
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Old 09-23-2009, 06:11 PM
 
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This is great, thank you. I wanted something but couldn't find anything. Must have not Googled right. Thanks!!
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Hot dogs
Old 09-25-2009, 03:38 PM
 
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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?
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Hot dogs
Old 10-03-2009, 06:45 PM
 
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That hot dog bun is a perfect example of real-life application! Thanks for sharing!


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Thank you parker!
Old 11-22-2009, 07:39 AM
 
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This helped a TON! Like, you have no idea!
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application of GCF
Old 11-25-2009, 05:40 AM
 
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I present GCF as a tool for simplifying fractions. So, any real life use of fractions, will be a real life application of GCF.
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Old 02-04-2010, 06:27 AM
 
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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?
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Another use
Old 02-16-2010, 10:29 PM
 
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Students find GCF all the time when reducing fractions. Anything that requires you to reduce a fraction or a ratio requires finding GCF.
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Old 11-12-2010, 09:47 PM
 
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Very good for daily life example! Very helpful
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Old 01-08-2013, 03:18 AM
 
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Thank you SO much, this really helped me!
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Hot Dogs and Buns
Old 06-12-2013, 07:14 AM
 
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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!
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I don't understand
Old 02-11-2014, 03:37 PM
 
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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.
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I understand now
Old 02-12-2014, 02:57 AM
 
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I did some research and now I understand.
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LCM real life situations
Old 08-21-2014, 08:32 PM
 
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very helpful.
i do this problem every year, but the "father of the bride" 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?
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