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By: pearldyn (offline)  Tuesday, March 02 2010 @ 09:44 AM CST (Read 12730 times)  
pearldyn

Here's another problematic question that always causes me headache.

3 similar oven toasters and 4 similar kettles cost $120.
2 such oven toasters and 1 such kettle cost $95.
Find the cost of an oven toaster.

Answer given: $52.00

If possible show me the model drawing as well.

Thank you in advance!!

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By: Jocelynliew (offline)  Tuesday, March 02 2010 @ 07:25 PM CST  
Jocelynliew

I have the same problems as you. I have 2 sons. One is in Pri 6 and the another in Pri 4. Everytime they ask me about the problem sums, I don't seem to understand. I find it too difficult. I will ask them to ask their daddy, but their daddy knows how to do but don't know how to explain to them. My son who is in Pri 6 don't like to draw model for the problem sums.

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By: AVE (offline)  Tuesday, March 09 2010 @ 03:04 AM CST  
AVE

hi here it is:

let x = the cost of each oven toaster
let y = the cost of each kettle

equation1: 3(x) + 4(y) = 120

equation2: 2(x) + y = 95

multiply equation 2 by 4: 4 times (2(x) + y = 95) and get equation 3:

equation3: 8(x) + 4(y) = 380

subtract equation 1 from equation 3:

8x + 4y = 380
- 3x + 4y = 120
-----------------------------
5x + 0 = 260

you get 5x = 260
x = 260/5
x= 52

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By: AVE (offline)  Tuesday, March 09 2010 @ 03:07 AM CST  
AVE

you can email me if you need personal tutor: ellaav@yahoo.com Wink

thanks.

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By: Charisse (offline)  Wednesday, May 05 2010 @ 11:17 AM CDT  
Charisse

Quote by: AVE

hi here it is:

let x = the cost of each oven toaster
let y = the cost of each kettle

equation1: 3(x) + 4(y) = 120

equation2: 2(x) + y = 95

multiply equation 2 by 4: 4 times (2(x) + y = 95) and get equation 3:

equation3: 8(x) + 4(y) = 380

subtract equation 1 from equation 3:

8x + 4y = 380
- 3x + 4y = 120
-----------------------------
5x + 0 = 260

you get 5x = 260
x = 260/5
x= 52



..if toaster's 52, what's the kettle? -9? Rolling Eyes

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By: pklua (offline)  Wednesday, May 05 2010 @ 09:17 PM CDT  
pklua

T= Oven Toaster
K=Kettle

3T + 4 K = $120----(1)
2T + 1 K = $95------(2)

Add the 2 equations together, you get 5T + 5K = $215
Hence, 1T + 1K = $43 ----(3)

(2) -(3),
1 T = $52

Even though the question does not sound logical, this is usually the way this type of questions are being solved. Razz

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By: Charisse (offline)  Thursday, May 06 2010 @ 10:11 AM CDT  
Charisse

Quote by: pklua

T= Oven Toaster
K=Kettle

3T + 4 K = $120----(1)
2T + 1 K = $95------(2)

Add the 2 equations together, you get 5T + 5K = $215
Hence, 1T + 1K = $43 ----(3)

(2) -(3),
1 T = $52

Even though the question does not sound logical, this is usually the way this type of questions are being solved. Razz



sure hope you are not one of those who put together our schools' exam papers.

how can maths b... illogical? it doesn't matter how the questions' usually solved. the answer's not logical. try explaining to the kid, who probably try to put the toaster's cost back into the statement to find the cost of the kettle. and wala! its a negative!! how cool is that?? Eek!

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By: Charisse (offline)  Thursday, May 06 2010 @ 10:15 AM CDT  
Charisse

oh btw, this problem came out in a P4 SA1 exam paper. they haven't learnt simultaneous equation Rolling Eyes

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By: CHEEKEE (offline)  Tuesday, May 11 2010 @ 03:23 AM CDT  
CHEEKEE

[b]Big Grin FOR ME ALSO I ALWAYS DON'T KNOW HOW TO DO THIS KIND OF QUESTION!!!! Frown [/b]

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By: nisalam (offline)  Monday, May 17 2010 @ 08:15 AM CDT  
nisalam

pklua is right. instead of using K and T, just draw out the kettles and toasters for your p4 kid. Once they see the 5 kettles and toasters, everything will fall in place. You avoid using simultaneous equations that way. This is called pre-algebra under the p4 maths syllabus.

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