Q&A - P5 Math

[Atan]

speedmaths.com:

Atan:

Pls assist to solve the flwg Qn:


Ben has a carton containing some red and green apples. if he adds in 10 red apples, 0.6 number of apples in the carton will be green apples. If he adds in 30 green apples, 3/4 of the number of apples in the carton will be green apples. How many apples are there in the carton?

Hi,

One possible Solution:
Using the Advanced Model Method
(or Bags and Boxes Method)

If he adds in 10 red apples,
0.6 of the apples in the carton will be green apples,
0.4 of the apples in the carton will be red apples

If he adds in 10 red apples, he could then
put all the green apples into 6 Bags, and
put all the red apples into 4 Bags.

Since he did not actually add in the 10 red apples, he actually has
6 Bags of green apples, and (4 Bags – 10) red apples

Green apples → 6 Bags
Red apples → (4 Bags – 10)

If he adds in 30 green apples,
3/4 of the apples will be green apples,
1/4 of the apples will be red apples,

If he adds in 30 green apples, he could then
put all the green apples into 3 Boxes, and
put all the red apples into 1 Box

Since he did not actually add in the 30 green apples, he actually has
(3 Boxes – 30) green apples, and 1 Box of red apples

Green apples → (3 Boxes – 30)
Red apples → 1 Box

From the above:

Green apples → 6 Bags → (3 Boxes – 30)
Red apples → (4 Bags – 10) → 1 Box

Green apples → 6 Bags → (3 Boxes – 30)
Green apples → 6 Bags + 30 → 3 Boxes ......(Row 1)

Red apples → (4 Bags – 10) → 1 Box
(x 3)
Red apples → (12 Bags – 30) → 3 Boxes .....(Row 2)

Row 2 = Row 1
(12 Bags – 30) → 3 Boxes → 6 Bags + 30 → 3 Boxes

12 Bags – 30 → 6 Bags + 30

(Subtract 6 Bags from both the right and left sides of the equation)

6 Bags – 30 → 0 Bag + 30

(Add 30 to both the right and left sides of the equation)

6 Bags – 0 → 0 Bag + 60
6 Bags → 60
1 Bag → 10

Green apples → 6 Bags
Red apples → (4 Bags – 10)

Ben has 10 Bags – 10 apples = (10 x 10) – 10 = 90 apples in the carton.

Hope this helps.

Cheers

speedmaths.com

PS.
Parents who wish to know more can look for the “PSLE Maths - Advanced Model Method” book.

.

THANKS very much, Speedmaths .

[favianboy]

smartmummy:

favianboy:

Need it urgently. Pls help to solve this qns, use assumption and not guess and check. Thanks


A total of 360 teachers and pupils participated in tree planting. Each teacher plated 3 trees and each group of 3 pupils planted 2 trees. If 520 tress were planted, how many pupils are there?

find the solution here
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=68&t=25129&p=951867&hilit=tree+planted#p951867

Thank you

[ponyo]

pupilview:

The enrolment of school A is twice of the enrolmentof school B.If 1260 pupils from school A transfer to school B,school B's enrolment would become thrice that of school A.How many pupils are there in school A?


Please help me to solve the above question using the model method.

Total remains constant.
Before : A:B= 2:1(total parts =3)
After: A:B=1:3 (total parts=4)

Common multiple of 3&4=12, ie
Before: A:B=8:4 (total=12 units)
After: A:B=3:9 (total=12 units)
8-3 units=5u were transferred from A to B
5units-->1260
1u=252
At first A has 8 units,=252*8=2016

Model drawing:
Before
A: [u][u][u][u] [u][u][u][u]
B: [u][u][u][u]

After
A: [u][u][u]
B: [u][u][u][u] [u] [u][u][u][u]

Diff=5u=1260

hope that helps...

[BlueBells]

Eva had 3 times as many books as Fiona. After Eva gave away 194 books and Fiona gave away 38 books, Fiona had twice as many books left as Eva. How many books did each girl have at first?


Thanks.

[tianzhu]

BlueBells:

Eva had 3 times as many books as Fiona. After Eva gave away 194 books and Fiona gave away 38 books, Fiona had twice as many books left as Eva. How many books did each girl have at first?


Thanks.

Hi

At first
Eva ------ 3 units
Fiona ------ 1 unit

Change
Eva ------ 194 (gave away)
Fiona ------ 38 (gave away)

In the end
Eva ------ 1 part
Fiona ------ 2 parts

3 units – 194 ------- 1 part
1 unit – 38 ------- 2 parts

Make the number of parts the same.

6 units – 388 ------- 2 parts
6 units – 388 ------- 1 unit – 38

5 units -------- 350
1 unit ------- 70

Eva@first -------- 210
Fiona @first ------- 70

Best wishes

[ponyo]

BlueBells:

Eva had 3 times as many books as Fiona. After Eva gave away 194 books and Fiona gave away 38 books, Fiona had twice as many books left as Eva. How many books did each girl have at first?


Thanks.

After:
E:[u]
F:[u] [u]

Since E gave away 194, and F gave away 38
Before:
E:[u] [u]+38 +[u] [u]+38 +[u] [u]+38
F:[u] [u]+38

[u]+38 +[u] [u]+38 +[u] [u]+38=194

5u+38*3=194
u=(194-114)/5=16

therefore, at first F has 16*2+38=70
E has 70*3=210

[smartmummy]

tianzhu:

BlueBells:

Eva had 3 times as many books as Fiona. After Eva gave away 194 books and Fiona gave away 38 books, Fiona had twice as many books left as Eva. How many books did each girl have at first?


Thanks.

Hi

At first
Eva ------ 3 units
Fiona ------ 1 unit

Change
Eva ------ 194 (gave away)
Fiona ------ 38 (gave away)

In the end
Eva ------ 1 part
Fiona ------ 2 parts

3 units – 194 ------- 1 part
1 unit – 38 ------- 2 parts

Make the number of parts the same.

6 units – 388 ------- 2 parts
6 units – 388 ------- 1 unit – 38

5 units -------- 350
1 unit ------- 70

Eva@first -------- 210
Fiona @first ------- 70

Best wishes

:thankyou:

[Oracle]

Help … please …


Everyday, Krishnan received 50 cents more than Edward for his allowance. However, Edward spent 80 cents more than Krishnan during their recess everyday. Over a period of time, Krishnan managed to save $100 and Edward managed to save $35.

(i) How many days would Krishnan take to save $100?
(ii) How much was Krishnan’s savings every day?

Thank you very much.

[jieheng]

Oracle:

Help ... please ...


Everyday, Krishnan received 50 cents more than Edward for his allowance. However, Edward spent 80 cents more than Krishnan during their recess everyday. Over a period of time, Krishnan managed to save $100 and Edward managed to save $35.

(i) How many days would Krishnan take to save $100?
(ii) How much was Krishnan's savings every day?

Thank you very much.

The amount of money that Krishnan save more than Edward every day = 0.50 + 0.80 = 1.30

Over a period of time , the amount of money that Krishnan save more than Edward = 100 - 35 = 65

i) No of days that Krishnan would take to save $100 = 65 / 1.30 = 50

ii) Krishnan's savings every day was = $100 / 50 = $2

[pupilview]

ponyo:

pupilview:

The enrolment of school A is twice of the enrolmentof school B.If 1260 pupils from school A transfer to school B,school B's enrolment would become thrice that of school A.How many pupils are there in school A?


Please help me to solve the above question using the model method.

Total remains constant.
Before : A:B= 2:1(total parts =3)
After: A:B=1:3 (total parts=4)

Common multiple of 3&4=12, ie
Before: A:B=8:4 (total=12 units)
After: A:B=3:9 (total=12 units)
8-3 units=5u were transferred from A to B
5units-->1260
1u=252
At first A has 8 units,=252*8=2016

Model drawing:
Before
A: [u][u][u][u] [u][u][u][u]
B: [u][u][u][u]

After
A: [u][u][u]
B: [u][u][u][u] [u] [u][u][u][u]

Diff=5u=1260

hope that helps...

My DD's reasoning:

A: 2u
B: 6u

6u - 2u = 1260
4u = 1260
u = 315

So School A's enrollment is (315x2)+1260= 1890.
:roll: :? Somebody please help.Which is the correct answer??