Finding least common denominator

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Fifth Grade Teachers Chatboard

Finding least common denominator

by Ally

Nov 30, 2010

Hi everyone! Do you guys have any tricks for teaching kids how to find the least common denominator? My kids are really struggling with this concept, and I am struggling to make it easier for them to understand. Thanks so much in advance! Allyson

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MarkB/GA As I feared, my numbers did not line up properly. If you send your email address to me, I'll send you a better looking copy in a Word doc. MarkB/GA

On 12/01/10, MarkB/GA wrote: > While I am waiting on my own teaching contract, I'm getting > to do a lot of substitute teaching and volunteer work. I > learned this technique for LCD. ...See More

Dec 1, 2010

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Ally Hey Mark. It sent your reply to my email and the formatting came out perfectly understanable! Thank you very much! I love the strategy for using this to find LCM too! Thanks!

Dec 1, 2010

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Glad I could help NFM On 12/01/10, Ally wrote: > Hey Mark. It sent your reply to my email and the formatting came out > perfectly understanable! Thank you very much! I love the strategy for > using this to find LCM too! Thanks!

Dec 2, 2010

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arachgold To help students understand what they are doing, draw a chart like below (draw a long vertical line after the 4 and 10.Have the students fill in the multiples and circle the least common multiple which is the same as the least common denominator.

For instance: Find the LCD of 4 and 10

4 ______________

10

Once...See More

Dec 2, 2010

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Francie Hi Mark,

Sounds great! Could you email with the Word doc?

Thanks,

Francie

On 12/01/10, MarkB/GA wrote: > As I feared, my numbers did not line up properly. If you send > your email address to me, I'll send you a better looking copy in > a Word doc. > MarkB/GA > > On 12/01/10, MarkB/GA wrote: ...See MoreHi Mark,

Sounds great! Could you email with the Word doc?

Thanks,

Francie

On 12/01/10, MarkB/GA wrote: > As I feared, my numbers did not line up properly. If you send > your email address to me, I'll send you a better looking copy in > a Word doc. > MarkB/GA > > On 12/01/10, MarkB/GA wrote: >> While I am waiting on my own teaching contract, I'm getting >> to do a lot of substitute teaching and volunteer work. I >> learned this technique for LCD. I may not be able to show the >> brackets properly, but I think I can show it well enough for >> you to get get idea. >> >> What is the least common denominator between 18 and 24? >> (This is also the highest common factor). >> >> Put 18 and 24 inside an "upside down" division bracket: >> >> >> | 18 24 >> ----------- >> >> Ask "What will divide evenly into both 18 and 24?" >> Some will know enough to say "6" but some may start with "2". >> I'll use 2 here. >> >> 2 | 18 24 >> ----------- >> 9 12 >> >> Ask "What will divide evenly into both 9 and 12?" >> >> The answer will be 3. >> >> 2 | 18 24 >> ----------- >> 3 | 9 12 >> ---------- >> 3 4 >> >> Ask "Besides 1, will any number divide evenly into both 3 and >> 4?" Of course, the answer is no because one of the numbers is >> prime. >> >> The numbers on the left of the brackets are multiplied >> together and this is your LCD. 2 X 3 = 6 >> >> By the way, if you multiply those on the left of the brackets >> and the numbers that are left over (3 and 4), you will have >> the Least Common Multiple (LCD). 2x3x3x4 = 72. >> >> To prove this for LCM: >> >> 1 2 3 4 >> --------------------- >> 18| 18 36 54 72 >> 24| 24 48 72 >> >> And, if you noticed back where we used the brackets, the >> factor we were left with on the 18 was 4 and on the 24 was 3, >> which is what you multiply each original number by to get >> find your LCM. >> >> MarkB/GA >> >> >> On 11/30/10, Ally wrote: >>> Hi everyone! Do you guys have any tricks for teaching kids >>> how to find the least common denominator? My kids are >>> really struggling with this concept, and I am struggling to >>> make it easier for them to understand. Thanks so much in >>> advance! Allyson

Dec 22, 2010

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