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#55390  09/14/09 07:00 PM
Help  5th grade math problem

Member
Registered: 03/11/09
Posts: 247

I know how I'd work this problem and I know the answer, but I'm not sure what methods are generally used in 5th gr and I don't want to confuse an issue. (btw, it's a bonus question and DS said they didn't go over how to do it.) ***About 7/10 of the US population (175,104,000) in 1991 believed saying A to be true. What was the total population?*** I'm so not good at 'teaching'. Even though I know how to do something, I'm not good at relaying the info in a way that makes sense. Guess I know where DS gets it . Can anyone offer up 5th grade ideas for how this type of problem is taught?

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#55391  09/14/09 07:05 PM
Re: Help  5th grade math problem
[Re: JDAx3]

Member
Registered: 12/14/07
Posts: 902

One of the possible solutions using Singapore math would be
1) You say that 7 units = 175,104,000
2) From that you calculate how much 1 unit is
3) Then you calculate what 10 units are equal to
_________________________
LMom

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#55393  09/14/09 07:09 PM
Re: Help  5th grade math problem
[Re: LMom]

Member
Registered: 04/22/09
Posts: 1000

That's what I would do, but I have no idea how 5th grade math teachers might do it these days.

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#55394  09/14/09 07:10 PM
Re: Help  5th grade math problem
[Re: LMom]

Member
Registered: 08/13/08
Posts: 744

Does he know how to crossmultiply?
I'd teach him 7/10=175,104,000/X
Then you multiply the 10 times the 175,104,000=7 times x
1,751,040,000=7x
Divide both sides by 7

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#55395  09/14/09 07:12 PM
Re: Help  5th grade math problem
[Re: LMom]

Member
Registered: 03/11/09
Posts: 247

One of the possible solutions using Singapore math would be
1) You say that 7 units = 175,104,000
2) From that you calculate how much 1 unit is
3) Then you calculate what 10 units are equal to
Thanks!! That's about where I was, but I wasn't sure if I was in the general grade area. Oh, and I love the 'teaching' instruction..."you say that 7 units...." LOL, I don't think I could mess this one up. Have a great day!

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#55399  09/14/09 07:17 PM
Re: Help  5th grade math problem
[Re: CAMom]

Member
Registered: 03/11/09
Posts: 247

Does he know how to crossmultiply?
I'd teach him 7/10=175,104,000/X
Then you multiply the 10 times the 175,104,000=7 times x
1,751,040,000=7x
Divide both sides by 7
Is crossmultiplication learned in 5th grade?? That was my very first thought, but I didn't think I could explain it even though I could do it. (I really have a hard time getting stuff out of my head and on to paper or in words.) I always remember "x over 100 is equal to is over of" from school, but that was many moons ago... Thanks!

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#55407  09/14/09 07:47 PM
Re: Help  5th grade math problem
[Re: Nautigal]

Member
Registered: 08/13/08
Posts: 744

I have a distorted frame of reference because my 7th graders used to take full algebra and our 6th graders took prealgebra. 8th graders all took geometry.

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