Q&A - PSLE Math

[cimman]

G Tan:

cimman:

[quote=\"G Tan\"]Can help in this sum<


Farid had $270 and Gopal had $192. Gopal spent twice as much as Farid. If Farid had twice as much money as Gopal after spending, much did Farid spend?

if you're open to using algebra and simultaneous equations, here's an approach:

http://i47.tinypic.com/2r5vjw1.png\">

with this table, and using simultaneous equations, you'll be able to solve all Transfer type problems. There will be extensions to the table, ie. more columns or more rows of (before, transfer, after) to cater for different scenarios, but basically, the logic and processing remains the same. It does not use heuristics, so it will not confuse the child on which heuristc to use.

Your answer is not the same as the answer in the book[/quote]ah yes, careless mistake. Should solve for u instead of p.

The equations remain the same:
270 – u = 2p ------------ 1
192 – 2u = p ----------- 2
384 – 4u = 2p
270 – u = 384 – 4u
3u = 114
u = 38

[G Tan]

cimman:

G Tan:

Can help in this sum<


Farid had $270 and Gopal had $192. Gopal spent twice as much as Farid. If Farid had twice as much money as Gopal after spending, much did Farid spend?

if you're open to using algebra and simultaneous equations, here's an approach:

http://i47.tinypic.com/2r5vjw1.png\">

with this table, and using simultaneous equations, you'll be able to solve all Transfer type problems. There will be extensions to the table, ie. more columns or more rows of (before, transfer, after) to cater for different scenarios, but basically, the logic and processing remains the same. It does not use heuristics, so it will not confuse the child on which heuristc to use.

Is there any way to do withoust using algerbra??? my DD ususlly got a hard time understanding algebra method...

[cimman]

G Tan:

cimman:

[quote=\"G Tan\"]Can help in this sum<


Farid had $270 and Gopal had $192. Gopal spent twice as much as Farid. If Farid had twice as much money as Gopal after spending, much did Farid spend?

if you're open to using algebra and simultaneous equations, here's an approach:

http://i47.tinypic.com/2r5vjw1.png\">

with this table, and using simultaneous equations, you'll be able to solve all Transfer type problems. There will be extensions to the table, ie. more columns or more rows of (before, transfer, after) to cater for different scenarios, but basically, the logic and processing remains the same. It does not use heuristics, so it will not confuse the child on which heuristc to use.

Is there any way to do withoust using algerbra??? my DD ususlly got a hard time understanding algebra method...[/quote]Tianzhu has provided the solution using modelling. You can have a look at that.
In P6, algebra is part of the syllabus. If you DD finds it hard to understand algebra, it would be good to use this holiday period to start her on the subject. The school will just spend 1 month or less teaching algebra in P6 and it will be quite stressful then.

While aglebra is not an easy topic, students can manage it if given the time (ie. 6 months) and the right environment (ie. no stress). Just teach slowly and let her assimilate it. The benefits are there. She will have one more tool in her bag of tricks. For your problem, it still manageable in modelling. There are some problems with a lot of transfers and that becomes quite tedious using modelling and sometimes there are a lot of boxes to split. So the algebra method can help out there.

Ultimately, you'll have to cross the algebra bridge when you come to P6. Best to start early to give your child more time to adjust to abstract concepts.

[dicoyote]

Beaker A and Beaker B contain some water.

If 46.5 ml of water is drained out from Beaker A, the volume of the water in Beaker A will be 60% that of the water in Beaker B.
If 35.2 ml of water is drained out from Beaker B, the volume of the water in Beaker B will be 85% that of the water in Beaker A.
What is the total volume of water in Beaker A and Beaker B?

Do I use algebra to tackle this question? Thanks in advanced

[MathIzzzFun]

dicoyote:

Beaker A and Beaker B contain some water.

If 46.5 ml of water is drained out from Beaker A, the volume of the water in Beaker A will be 60% that of the water in Beaker B.
If 35.2 ml of water is drained out from Beaker B, the volume of the water in Beaker B will be 85% that of the water in Beaker A.
What is the total volume of water in Beaker A and Beaker B?

Do I use algebra to tackle this question? Thanks in advanced

Hi

If 46.5ml drained from A, then volume in A :volume in B = 60:100-->3u:5u
So,
total volume in A : total volume in B --> 3u + 46.5 : 5u -- total volume --> 8u + 46.5

If 35.2ml drained from B, volume in A: volume in B
= 3u + 46.5 : 5u - 35.2
= 100 : 85
= 20 : 17

cross-multiply/equalize
51u + 790.5 = 100u - 704
49u --> 1494.5
1u --> 30.5

Total volume in A & B --> 8 x 30.5 + 46.5 = 290.5 ml

cheers.

[notfreemom]

tianzhu:

notfreemom:

Hi I need help for this question

Nanyang sa1
Q15 paper 2
Mr Yama went shopping and bought 8 shirts from the first shop. Then, he bought 3 more identical shirts at $42.50 each from the second shop. The average cost of all his shirts was decreased by $1.50. What was the total cost of the 11shorts?

Thanks

Hi

Decrease in average cost ------ 1.5*8 ------- 12

This $12 is distributed among the 3 new shirts

12/3 ------- 4

Revised average cost ------ 42.50 + 4 ------- 46.50

Total cost ------- 46.50*11 ------- 511.50

Best wishes

Thanks tianzhu!

[notfreemom]

Hi,

I need help for this question.
Red Swastika Prelim 2012
Paper 2 Q 15.

Eugene, Freddy and George had some playing cards. Freddy had 200 more playing cards than Eugene. Geroge had 3/4 the number of cards Freddy had. After George lost 1/6 of his cards to Eugene, he had 320 fewer cards than Eugene. What was the ratio of the number of cards Eugene had to the number of cards Freddy had to the number of cards George had in the end?

My dd asnwer is 61:72:45 but the asnwer given is 97:104:65.
Thanks.

[tianzhu]

notfreemom:

Hi,

I need help for this question.
Red Swastika Prelim 2012
Paper 2 Q 15.

Eugene, Freddy and George had some playing cards. Freddy had 200 more playing cards than Eugene. Geroge had 3/4 the number of cards Freddy had. After George lost 1/6 of his cards to Eugene, he had 320 fewer cards than Eugene. What was the ratio of the number of cards Eugene had to the number of cards Freddy had to the number of cards George had in the end?

My dd asnwer is 61:72:45 but the asnwer given is 97:104:65.
Thanks.

Hi

The given answer is correct.

Consider this at the start.

Eugene ------ 8 units
Freddy ------ 8 units + 200
George ------ 6 units + 150

In the end

Eugene ------ 9 units + 25 ------ 970
Freddy ------ 8 units + 200 ------ 1040
George ------ 5 units + 125 ------ 650

9 units + 25 ------- 5 units + 125 +320
1 unit ------- 105

The ratio ------- 97:104:65

Best wishes

[MathIzzzFun]

notfreemom:

Hi,

I need help for this question.
Red Swastika Prelim 2012
Paper 2 Q 15.

Eugene, Freddy and George had some playing cards. Freddy had 200 more playing cards than Eugene. Geroge had 3/4 the number of cards Freddy had. After George lost 1/6 of his cards to Eugene, he had 320 fewer cards than Eugene. What was the ratio of the number of cards Eugene had to the number of cards Freddy had to the number of cards George had in the end?

My dd asnwer is 61:72:45 but the asnwer given is 97:104:65.
Thanks.

Hi

At first:
Eugene --> 8 units
Freddy --> 8 units + 200
George --> 6 units + 150 ----- 1/6 --> 1u + 25

after George lost 1/6 of his cards to Eugene,
Eugene --> 9 units + 25
Freddy --> 8 units + 200
George --> 5 units + 125

George had 320 cards fewer than Eugene
5 units + 125 + 320 = 9 units + 25
1 unit --> 105

In the end,
Eugene --> 970
Freddy --> 1040
George --> 650

ratio Eugene : Freddy : George = 97 : 104 : 65

cheers.

[notfreemom]

Thanks mathizzzfun and Tianzhu.

I knew my mistake now.
Thanks again.