Q&A - P4 Math

[iFirefly]

ksi:

Champion:

:?: need help with this question as well :thankyou:


There were twice as many boys as girls at the school hall.
After 15 girls had left, the number of boys was thrice the number of the remaining girls. How many students wee there at the school hall?

http://i41.tinypic.com/2d1sg8z.jpg\">

Hi ksi,
From the model provided, it seems to me that total number of girls was 45 (u=30.. u+15.. 30+15), and total number of boys was 90 (45x2), hence total number of students at the hall should be 135 (45+90)?
But 120 seems right too (u=30.. 30x4), from the second model that you drew for the boys (the top most bar).
Appreciate your clarification.. Thanks!

[smartmummy]

How many students were at hall is 135.

After15 girls left,How many students are in the school now is 120.
According the qn the answer is 135.

firefly38:

ksi:

[quote=\"Champion\"]:?: need help with this question as well :thankyou:

There were twice as many boys as girls at the school hall.
After 15 girls had left, the number of boys was thrice the number of the remaining girls. How many students wee there at the school hall?

http://i41.tinypic.com/2d1sg8z.jpg\">

Hi ksi,
From the model provided, it seems to me that total number of girls was 45 (u=30.. u+15.. 30+15), and total number of boys was 90 (45x2), hence total number of students at the hall should be 135 (45+90)?
But 120 seems right too (u=30.. 30x4), from the second model that you drew for the boys (the top most bar).
Appreciate your clarification.. Thanks![/quote]

[Charnic]

I have a question. It goes like this :


I have 5026g of flour in a bag. I bot another packet which contain 4157g. If i would transfer some flour from the bag to the packet, the mass of flour remaining in the bag becomes twice the mass left in the packet. How much flour is left in the packet in the end?

I solved the question by using 5026+4157, thereafter divide by 3 to get the end result of flour left. However, i have been teaching my gal to use the transfer method, ( like what onsponge is doing), but i am stuck in the model. Can someone pls help to draw a clear model for the above ? Greatly appreciated! TIA

[chloecube]

MathIzzzFun:

chloecube:

Need help on this:

John had 4 times as many marbles as Brandon. After John gave 28 marbles away, Brandon had twice as many marbles as John. How many more marbles did John have than Brandon.
Thks

hi

MD approach ...

http://www.flickr.com/photos/62167097@N02/6880430857/in/photostream/

cheers.

good morning! thks!

[tianzhu]

CNS:

I have a question. It goes like this :


I have 5026g of flour in a bag. I bot another packet which contain 4157g. If i would transfer some flour from the bag to the packet, the mass of flour remaining in the bag becomes twice the mass left in the packet. How much flour is left in the packet in the end?

I solved the question by using 5026+4157, thereafter divide by 3 to get the end result of flour left. However, i have been teaching my gal to use the transfer method, ( like what onsponge is doing), but i am stuck in the model. Can someone pls help to draw a clear model for the above ? Greatly appreciated! TIA

Hi

Please check with your source.

tranfer from the packet to the bag? or tranfer from the bag to the packet ?

Best wishes

[Charnic]

Sorry, is packet to the bag. Pls assist to draw the model. TIA.

[tianzhu]

CNS:

Sorry, is packet to the bag. Pls assist to draw the model. TIA.

Hi

A student should take note that that the total amount of flour remains the same before and after.

Bag ----- 2 units
Packet ----- 1 unit

3 units ------ 9183

1 unit ------ 3061 (This is the amount of flour left in the packet).

Best wishes

[Charnic]

But if we want to use cut and transfer method, possible ? When I told my gal about the way you mentioned, she asked me to draw the model on pre and post, that is where i am stuck ? I am also quite confused when to use what method ? Sigh.. :oops:

[tianzhu]

CNS:

But if we want to use cut and transfer method, possible ? When I told my gal about the way you mentioned, she asked me to draw the model on pre and post, that is where i am stuck ? I am also quite confused when to use what method ? Sigh.. :oops:

Hi

MD is one of the many problem solving heuristics in primary school maths. It’s not the only one.

From the way your question is worded, there is no necessity to go further than throwing 2 boxes for bag and 1 box for packet.

The question asks for the amount of flour left in the packet which is represented by 1 box.

If the question asks “How much flour was transferred from the packet to the bag? Then, it’s is (4157-3061) which is 1096.

A student may want to add some arrows to show the transactions during the transfer, it’s possible, but the issue is “Is it necessary?”

Best wishes

[MathIzzzFun]

CNS:

But if we want to use cut and transfer method, possible ? When I told my gal about the way you mentioned, she asked me to draw the model on pre and post, that is where i am stuck ? I am also quite confused when to use what method ? Sigh.. :oops:

Hi

here's the model...

http://i44.tinypic.com/1z5kndj.jpg\">

as mentioned by tianzhu, MD is not the only approach to problem solving and in this case, using the MD to show the transfer is a little cumbersome. The better way is to see that the total amount of flour remained the same and after the transfer, there were 3 units of flour in total -> which is the solution provided by tianzhu.

cheers.