Q&A - P5 Math

[PapayaDad]

carol73:

Hi pls help


Trianne baked 4 cakes. She kept 1/3 of a cake for herself and gave the rest to her friends, if each of her friends received 1/3 of a cake. how many friends received the cake?

4 cakes. each cake cut into 3 parts.
in total there are 12 parts.
she kept 1 part for herself.
left 11 parts. gave to 11 friends... each friend get 1 part (ie. 1/3 of a cake)
answer is 11.

[PapayaDad]

swordtail:

Sandra has twice as many apples as oranges at first. She removes 4 apples and 3 oranges each time. In the end, there are 18 apples and 1 orange left. What is the total number of fruits Sandra had at first?

[18] keep adding 4
[01] keep adding 3

[18][22][26][30][34][38][42][46][50]
[01][04][07][10][13][16][19][22][25]

[ChewingPencilLine]

swordtail:

Sandra has twice as many apples as oranges at first. She removes 4 apples and 3 oranges each time. In the end, there are 18 apples and 1 orange left. What is the total number of fruits Sandra had at first?


Tianzhu,
tks for the solution. But could you draw the model drawing? Still a bit confused, like how do you get the 6 units? tks

tks for your solution

\"18 + 4 units ------ 2 parts

1 + 3 units ------ 1 part\"

you get 2 + 6 units by multiplying the second line by 2
i.e. 2 + 6 units ------ 2 parts

Therefore, 18 + 4 units = 2 + 6 units since both are equivalent to 2 parts.

[tianzhu]

swordtail:

Tianzhu,
tks for the solution. But could you draw the model drawing?

Hi

Good Morning.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7406/8722172780_0c21e35195_z.jpg\">

[chloecube]

school teacher method look complex to me, any one can help with model or perhaps other simpler method for this sum?


Muna and Rita had 360 seashell. Muna gave 4/7 of her seashells to Rita. in return, rita gave 2/5 of her total number of seashells to Muna. then they have an equal number of seashells each. how many seashells did each of them have at first?

[andyle.024255sg]

chloecube:

school teacher method look complex to me, any one can help with model or perhaps other simpler method for this sum?


Muna and Rita had 360 seashell. Muna gave 4/7 of her seashells to Rita. in return, rita gave 2/5 of her total number of seashells to Muna. then they have an equal number of seashells each. how many seashells did each of them have at first?

How about working backwards?
At the end each have 180

After Rita gave 2/5, she had left 3/5, right?
3/5 of Rita -> 180
1/5 of Rita -> 60
5/5 of Rita -> 300
At that time, Muna had 60 (sum is 360)

Muna gave 4/7, hence she had left 3/7 (this is 60ss)
3/7 of Muna -> 60
7/7 of Muna -> 140
So at the beginning, Muna had 140
Rita had 360-140=220

Check:
Muna and Rita
Beginning: 140 and 220
After Muna gave 4/7 (80ss): 60 and 300
After Rita gave 2/5 (120ss): 180 and 180

Maybe drawing model better?

[doraemo]

The Right Equation:

carol73:

hi

pls help

1) Jamie spent $6 less than 4/7 of her money on a dress. She spent $6 more than 1/2 of ther remaining amount of money on a blouse. If she had $24left, how much money did she have at first

this qn uses drop-down model + working backwards. http://i40.tinypic.com/2ceqnm9.jpg\">

[/quote]

Hi The Right Equation
Would like to seek your clarification/explanation of the rationale behind in drawing the models in this manner.

[chloecube]

andyle.sg:

chloecube:

school teacher method look complex to me, any one can help with model or perhaps other simpler method for this sum?


Muna and Rita had 360 seashell. Muna gave 4/7 of her seashells to Rita. in return, rita gave 2/5 of her total number of seashells to Muna. then they have an equal number of seashells each. how many seashells did each of them have at first?

How about working backwards?
At the end each have 180

After Rita gave 2/5, she had left 3/5, right?
3/5 of Rita -> 180
1/5 of Rita -> 60
5/5 of Rita -> 300
At that time, Muna had 60 (sum is 360)

Muna gave 4/7, hence she had left 3/7 (this is 60ss)
3/7 of Muna -> 60
7/7 of Muna -> 140
So at the beginning, Muna had 140
Rita had 360-140=220

Check:
Muna and Rita
Beginning: 140 and 220
After Muna gave 4/7 (80ss): 60 and 300
After Rita gave 2/5 (120ss): 180 and 180

Maybe drawing model better?

so much clearer now
:thankyou:

[Awonder]

Oldschool:

Awonder:

There were a total of 930 boys and girls at a carnival. After 4/5 of the boys and 3/4 of the girls left, there were 120 more girls than boys that remained. How many girls were there at the carnival at first?

Hi,

http://i41.tinypic.com/1819ix.jpg\">

Regards

Thank you for the answer and Tianzhu too.

[veraclari]

Hi all, need help as I don’t understand why a method or step is done.

Julian has 5/7 as many marbles as Kenneth. Kenneth has 2/3 as many marbles as Alex. If Alex has 105 more marbles than Kenneth, how mamy more marbles than Julian does Alex Have?

Solution step 1:
5/7 = 10/14 ( convert by multiplying by 2)

2/3 = 14/21 (convert by multiplying by 7)

I know they do the above to find difference in units between Kenneth and Alex. BUT how do we Detemine or Know that must be Multiplied by X 2 & X 7??
Why 2 & 7 ?
Thanks! !!