I need help with a CWP 3 question

[Guest BugabooNut]

Here is the question:

 

The sum of A and B is 4215 greater that C. C is 1833 less than A. What is B?

 

My husband and I know how to solve this using algebra.. but Singapore would have us do it using bar graphs and simple addition and subtraction.

 

Anyone know how to explain this to a level 3 student?:confused:

 

Thank you!

[plain jane]

This is how we set up the bar diagram for this problem:

 

[----------------A----------------][--------------B--------------]

 

[------C-------]<-----1833----->[------------???--------------]

___________ <-------------------------4215----------------->

 

 

From setting it up this way, dd was able to see what she needed to do to find the value of B. Not sure if this is any help but it worked for us. :tongue_smilie: 4215-less the difference between C and A= the answer (2382).

Edited February 3, 2011 by plain jane
added one last part to the diagram for clarification

[Guest BugabooNut]

Thank you! I can now "see" it!

 

I can say, without a doubt, that homeschooling is the greatest education I ever got!:001_smile:

[plain jane]

Thank you! I can now "see" it!

 

I can say, without a doubt, that homeschooling is the greatest education I ever got!:001_smile:

 

Yup. :) I was never taught anything like SM bar diagrams when I was in school. It's been a whole new way of thinking about math, that's for sure.

[JadeOrchidSong]

A+B-4215=C

A=C+1833

 

Then

A=C+4215-B

So

 

C+1833=C+4215-B

 

Then B=4215-1833

 

But I agree that the bars are better.

[Guest BugabooNut]

That is how my husband and I figured it out. The problem is that I am teaching this to my 9 year old dd.

 

This question came out of the CWP Primary 3 book:001_huh: They expected us to be able to come up with that bar method. I just couldn't figure it out.

 

Thanks for taking the time to help!

[Dana]

The bar models were really foreign to me when I started with the books. We're doing CWP 3. I finally decided that I'd work the problems using bar models ahead of my son so if he got stuck, I could quickly help. I'm almost done with the book.

 

What I find fascinating is that some of the problems can be solved much faster with bar models than with algebra. The bar models also lead to a great transition to algebra. I plan on starting with some variables later this year or next and doing some algebra to solve the word problems.