Q&A - P4 Math

[snowball]

Nebbermind:

snowball:

how to explain to DD ;


3/5 divide by 3 is the same as 3/5 multiply by 1/3 ???

I think you should teach her the concept of fractions and 3/5 is actually

1/5 + 1/5 + 1/5

and if divided by 3, u get 1/5.

The answer may be ths same but for younger kids, it's good for they to be able to visualize why they are the same.

Same for multipication. 3 of 5 and 5 of 3 means very different things even thought their answers are the same.

Dear Nebbermind, using your suggestion above ( 1/5 +1/5+ 1/5) is indeed a very simple but useful explaination .

However, how do i explain;

3/8 divide by 3/5 is = 3/8 x 5/3 :?

[Nebbermind]

Snowball


See if http://www.homeschoolmath.net/teaching/f/division_fractions.php makes any sense to you.

[snowball]

Nebbermind:

Snowball


See if http://www.homeschoolmath.net/teaching/f/division_fractions.php makes any sense to you.

:thankyou: EASIER NOW! :rahrah:

[BigDevil]

snowball:

:thankyou: :please:
for this type of questions, how do we see (beginning) how many units to draw in the model? eg, for the above qn, 6units to draw for the men :?

You will realise what model to draw if you can think of this question in fractions.

At first, there were twice the number of men as women. That's the same as saying number of women is 1/2 of men.

Likewise, at the end, number of women is 1/3 of men.

Changing to same denominator, you get 3/6 at first, and 2/6 at the end.
You can then proceed to solve the problem with fractions (1/6 = 12),
or draw the model with 6 units for men.

You can also draw the following alternate model for this question without realising you need to draw 6 units for men:
http://i48.tinypic.com/iznno9.jpg\">

[snowball]

BigDevil:

snowball:

John is 34 yrs old n his son is 4 yrs old now. In how many yrs time will John be 4 times as old as his son?

http://i45.tinypic.com/35mo0fk.jpg\">

:scratchhead: why 3u is 30? :scratchhead: :?

[snowball]

snowball:

which of the following is the best estimate of 55x249?


a)50x250 ?
or
b)60x250 ?

ans sheet is (a) but i think is( b)

Is it because ;

i) it is easier to multply by 50 than 60 so we use 50 x250 ? :scratchhead:

or

ii) since it is multiplication ( instead of addition ) the estimate is more accurate to use 50 instead of 60 ? :scratchhead:

[snowball]

BigDevil:

snowball:

:thankyou: :please:
for this type of questions, how do we see (beginning) how many units to draw in the model? eg, for the above qn, 6units to draw for the men :?

You will realise what model to draw if you can think of this question in fractions.

At first, there were twice the number of men as women. That's the same as saying number of women is 1/2 of men.

Likewise, at the end, number of women is 1/3 of men.

Changing to same denominator, you get 3/6 at first, and 2/6 at the end.
You can then proceed to solve the problem with fractions (1/6 = 12),
or draw the model with 6 units for men.

You can also draw the following alternate model for this question without realising you need to draw 6 units for men:
http://i48.tinypic.com/iznno9.jpg\">

Dear BigDevil, your explanation is very clear & interesting, I'm getting more and more interested to do more of this types of qns before sharing with my dd :please:

Could you also show how to derived ( the workings ) for the alternate model, i would like to learn too :evil:

[BigDevil]

snowball:

:scratchhead: why 3u is 30? :scratchhead: :?

John is 34 while his son is 4 now.
The age difference is 34 - 4 = 30.

John will ALWAYS be 30 years older than his son.
Hence, 3u = 30.
u = 10.

John is 4 times as old as his son when the son is 10 yrs old in 6 years time.

Check:
After 6 years,

John is 34 + 6 = 40
Son is 4 + 6 = 10

[BigDevil]

snowball:

Dear BigDevil, your explanation is very clear & interesting, I'm getting more and more interested to do more of this types of qns before sharing with my dd

You are very welcome.
I am glad to help as this will help prepare me to guide DD when she goes to P4 next year.

Like for this question, I somehow came to the conclusion that the problem can best be represented by drawing a model of 6 units.
It wasn't until you asked, then that forced me to give it a deeper thought and came up with the explanation in fractions.

snowball:

Could you also show how to derived ( the workings ) for the alternate model, i would like to learn too :evil:

http://i48.tinypic.com/97sl1s.jpg\">

[COOKIE64]

how do i help my ds from making careless mistakes?? he got 85 for maths sa2 and lost 15 marks for being very careless? just copy wrong figures??