Q&A - P4 Math

[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??

[snowball]

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??

my girl too, lose marks due to carelessness. MCS no. written on the paper is correct, but shaded wrong no. !!! :slapshead: :stupid:
of course , i felt heart pain, but is also good to let her feel the pinch herself= expensive lesson to learn for her which i dont think we can help much, it all depends on themselves

[pchong]

snowball:

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??

my girl too, lose marks due to carelessness. MCS no. written on the paper is correct, but shaded wrong no. !!! :slapshead: :stupid:
of course , i felt heart pain, but is also good to let her feel the pinch herself= expensive lesson to learn for her which i dont think we can help much, it all depends on themselves

At least, they are able to realize their mistakes now and learn from it and not wait till PSLE which will then be too late!

[pchong]

I have seen a number of posts here asking for maths solution....ur dc are still busy practicing on maths problems even after exam? I can't get mine to do any work as he said now is holiday season, suppose for him to rest and relax.

[snowball]

pchong:

I have seen a number of posts here asking for maths solution....ur dc are still busy practicing on maths problems even after exam? I can't get mine to do any work as he said now is holiday season, suppose for him to rest and relax.

Is indeed and actually very difficult for them to do revision during the\" post exam period \" :stompfeet:

i m the one \"brushing\" up before i can teach my dd....cos i still cant find a passionate maths tutor for her and many parents here have shared tat Pr5's maths is a BIG JUMP :nailbite: so i plan to revise with dd on her weaker topics during this holidays.

So, pchong, if your dc is already >85 in her pr 4 sa2, i think u can relax a bit bit la :please: