Q&A - P5 Math

[cimman]

carol73:

thanks, btw, there are so many methods, how do you know which method to use for what type of questions


my girl is quite weak in choosing which method to use based on qn, ie when to use model, units method, guess and check and subsitution?

actually, there is a way to get around all the different methods. That way is through algebra. The reason why we have all the different methods is because children do not know how to use algebra. However, if your child is familiar with algebra, the relationships can be easily resolved without the use of different heuristics.

Having said that, the traditional way to using algebraic equation is not easy to teach, since most of the derivation of the equation is mental. Only the final equations are written down. The process of how the equations are derived are totally mental. I've developed an approach that guides students to the final equations through a step by step approach based on a visual analysis technique. All analysis are done on pen and paper, so the equation derivations can be easily followed by students. I do conduct workshops on this technique.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=43&t=32278&start=190

[Jamesbond]

Thanks for all your help.

[Jamesbond]

http://i50.tinypic.com/fcv5hc.jpg\">

Help needed.

[newuser]

jieheng:

kavisuresh:

Hi,

Pls help to solve .
1.Tins X,Y,Z each contained some chocolate powder. Mr.John transferred 1/8 of the chocolate powder from tin X to tin Y , then scooped 1/8 of the chocolate powder from tinY into tin Z and finally transferred 1/8 of the chocolate powder from tin Z to tin X. Now there are 49g of chocolate powder in each tin. How much chocolate powder was there in each tin at first ?

Thank you.

After transferred 1/8 of the chocolate powder from tin Z to tin X , tin Z left 7/8 . tin Z --> 7u and tin Z transferred 1u to tin X

In the end


I am lost in explaining to this DS.
Anyone can help to draw MD for us to visualize?


X 7u (49g)
Y 7u (49g)
Z 7u (49g)

Before transferred 1/8 (1u) of the chocolate powder from tin Z to tin X
X 6u
Y 7u
Z 8u

After transferred 1/8 of the chocolate powder from tin Y to tin Z , tin Y left 7/8 . 7/8 --> 7u and tin Y transferred 1u to tin Z

Before transferred 1/8 (1u) of the chocolate powder from tin Y to tin Z
X 6u
Y 8u
Z 7u

After transferred 1/8 of the chocolate powder from tin X to tin Y , tin X left 7/8 . 7/8 --> 6u , as 6u is not divisible by 7 , change tin X 6u --> 6u*7 = 42u , tin Y 8u --> 8u*7 = 56u and tin Z 7u --> 7u*7 = 49u

New ratio
X 42u
Y 56u
Z 49u

7/8 --> 42u ==> 1/8 --> 6u , tin X transferred 6u to tin Y

At first
X 48u
Y 50u
Z 49u

In the end , total powder = X + Y + Z = 3*49 = 147

48u + 50u + 49u --> 147
147u --> 147
1u --> 1

At first
X 48u --> 48g
Y 50u --> 50g
Z 49u --> 49g

[snowball]

what is the sum of all even no. from 21 to 80 ?

any short cut formula for above qn?
TIA

[PapayaDad]

The first even number is 22 and the last is 80 and they total 102.

The second and second last 24 and 78 and they total 102 also.
And the list goes on and we can make multiple pairs totalling 102.
There are 30 even number, so we can make 15 pairs (last pair is 50 and 52).
15 x 102 = 1530

[snowball]

PapayaDad:

The first even number is 22 and the last is 80 and they total 102.

The second and second last 24 and 78 and they total 102 also.
And the list goes on and we can make multiple pairs totalling 102.
There are 30 even number, so we can make 15 pairs (last pair is 50 and 52).
15 x 102 = 1530

How to calculate there r 30 even no.?
Any shortcut formula?

[PapayaDad]

From 21 to 80 there are 60 numbers.

Half is odd, half is even.

[smartmummy]

pls guide me.

how to do the following type qns
rearrange the following fractions in ascending order
3/4,7/8,5/6,11/12,8/9
for small numbers we can find the least common mutiple, then can rearrange.For big numbers also have to do like that or any short cut available?.
thanks in advance.

[PapayaDad]

How far are they from 1? the further they are from 1 the smaller they are, the nearer to 1 they are bigger. So,


3/4 is 1/4 a way from 1
7/8 is 1/8 away from 1
5/6 is 1/6 away from 1
11/12 is 1/12 away from 1
8/9 is 1/9 from 1

so,
11/12 is biggest
3/4 is smallest

can work out the rest already