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Need help...Primary M. Challenging WP 3?


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OK, so I have humbly hit a wall! Yikes!

Singapore Primary Math Challenging word problems book 3 page 8 # 13 and then again page 10 #19.

 

The sum of A and B is 5215 greater than C. C is 1833 less than A. What is B?

 

How do I teach this NON algebraically?

 

Also:

Jason and Bob have 193 marbles altogether. Bob has 47 fewer marbles fewer than Jason. If Jason gives 15 marbles to Bob, how many more marbles will Jason have than Bob?

 

Again, how do I teach a solution that is non-algebra? Hopefully this is much simpler than I am realizing.... or else I am in trouble the rest of this book.... we are doing this for fun as we have completed all our other math for the year!

 

Thanks!

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OK, so I have humbly hit a wall! Yikes!

Singapore Primary Math Challenging word problems book 3 page 8 # 13 and then again page 10 #19.

 

The sum of A and B is 5215 greater than C. C is 1833 less than A. What is B?

 

How do I teach this NON algebraically?

 

Also:

Jason and Bob have 193 marbles altogether. Bob has 47 fewer marbles fewer than Jason. If Jason gives 15 marbles to Bob, how many more marbles will Jason have than Bob?

 

Again, how do I teach a solution that is non-algebra? Hopefully this is much simpler than I am realizing.... or else I am in trouble the rest of this book.... we are doing this for fun as we have completed all our other math for the year!

 

Thanks!

 

You use bar models. I'm not sure how to draw them here though. I;ll try for the second and then come back to the first if no one else has, meanwhile giving this a bump.

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O

 

Also:

Jason and Bob have 193 marbles altogether. Bob has 47 fewer marbles fewer than Jason. If Jason gives 15 marbles to Bob, how many more marbles will Jason have than Bob?

 

Again, how do I teach a solution that is non-algebra? Hopefully this is much simpler than I am realizing.... or else I am in trouble the rest of this book.... we are doing this for fun as we have completed all our other math for the year!

 

Thanks!

 

 

[-----------------------------------------------------] J and B (193)

[--------------------------] 1/2 less 47 of above = B (73)

 

 

[--------------------------------] 73 + 15 = 88 marbles Bob

 

[--------------------------------------------] 105 marbles Jason

 

 

[-------] difference between 105 and 88: 13 marbles

 

 

(I think! If no errors on my part! In reality I'd try to line up the relevant parts of the bars better but cannot figure out how to do that here. Also there are often many ways to get the answer in multistep problems, I didn't necessarily choose the best, but was trying to show the bar models use.)

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For the second problem:

 

The difference between J and B is 47. If J gives B 15 marbles, the difference is reduced by those 15 marbles J loses. But since B gains 15 marbles, the difference between J and B is also reduced by 15. So the total reduction in the difference is 30.

 

Answer must be 17.

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For the second problem:

 

The difference between J and B is 47. If J gives B 15 marbles, the difference is reduced by those 15 marbles J loses. But since B gains 15 marbles, the difference between J and B is also reduced by 15. So the total reduction in the difference is 30.

 

Answer must be 17.

 

Yes. I agree. I did make an error above. This time I did yet a different way:

 

At point that it shows Bob with 73, that means Jason has 120.

When J gives B 15 he has 105 left. B gains 15 and has 88, and the difference between 105 and 88 is 17.

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