2009 Maths Question which Adult also duno!

[Limsgp]

And Bill Gates is a school dropout?

Well, it doesn't matter what you score in PSLE, or A level.

Just got to take note that it is which direction you go after that that counts.

A car salesman makes 8k a month.
A stock broker makes 12k a month
A property agent makes 20k a month.

Go figure that out.

Engineers, accountants, lawyers, doctors make much less than that. This is just a general statement. There are exception, of course.

 

[aryanto]

And Bill Gates is a school dropout?

university drop-out

 

[castwind]

I did my PSLE more than 20 years ago, and I think the method that was taught to me still works today. Don't think about algebra or model. Use trial and error. I am not joking.

Try this.

Assume Jim has 20 sweets, after Jim ate 12, there will be 8 left. Then that means Jim has 8 x 7 = 56 chocolates.
Ken ate 18 chocolates. That means 38 left. If that is true, then there are 38/4 = 9.5 sweets. Fraction is okay. Just leave it for the moment. It is to help us to agar-agar the results.

Now assume Jim has 30 sweets, after Jim ate 12, there will be 18 left. Then that means there are 18 x 7 = 126 chocolates.
Ken ate 18 chocolates. That means 108 left. If that is true, then there are 108/4 = 27 sweets. Fraction is okay. Actually we are close to getting the correct estimate as 27 is very close to 30.

Now assume Jim has 32 sweets, after Jim ate 12, there will be 20 left. Then that means there are 20 x 7 = 140 chocolates.
Ken ate 18 chocolates. That means 122 left. If that is true, then there are 122/4 = 30.5 sweets. Fraction is okay. Actually we are even closer now to getting the correct estimate as 30.5 is very close to 32.

Now assume Jim has 34 sweets, after Jim ate 12, there will be 22 left. Then that means there are 22 x 7 = 154 chocolates.
Ken ate 18 chocolates. That means 136 left. If that is true, then there are 136/4 = 34 sweets. The result is the same as my assumption. So 34 is correct!

But since Jim and Ken each has 34 sweets, so there are 68 sweets total, and 154 x = 308 chocolates.

No need for simultaneous equation. Using this method may be even faster than using simultaneous eqn. Anyone need a PSLE maths tutor?

 

[Ah Pao]

I did my PSLE more than 20 years ago, and I think the method that was taught to me still works today. Don't think about algebra or model. Use trial and error. I am not joking.

It's called "Guess and Check". One of the several heuristics taught to our primary school children, which Model Drawing is one of them. It is actually a theoretically sound method of solving mathematical problems.

 

[drakon09]

Yep, that's trial-and-error. (In fact, I did use this at my PSLE oh so many years ago).

Personally I've always preferred algebra, even as a kid.

Probably because I quite OCD when it comes to drawing boxes, so takes too much time. :bsmilie:

 

[Daedalus Trent]

well, much of what you learn at higher levels, also no use.

someone once said to me, and i found it true, was that the brain can be trained. it might not be trained at the things that are necessary in life; but using it to think in various ways, that helps.

Yup, totally agree on that :think:

If you can learning useless stuff for an examination...you're definitely capable of learning useful stuff. At least, that's what Universities think, imho.

 

[lancey]

I did my PSLE more than 20 years ago, and I think the method that was taught to me still works today. Don't think about algebra or model. Use trial and error. I am not joking.

Try this.

Assume Jim has 20 sweets, after Jim ate 12, there will be 8 left. Then that means Jim has 8 x 7 = 56 chocolates.
Ken ate 18 chocolates. That means 38 left. If that is true, then there are 38/4 = 9.5 sweets. Fraction is okay. Just leave it for the moment. It is to help us to agar-agar the results.

Now assume Jim has 30 sweets, after Jim ate 12, there will be 18 left. Then that means there are 18 x 7 = 126 chocolates.
Ken ate 18 chocolates. That means 108 left. If that is true, then there are 108/4 = 27 sweets. Fraction is okay. Actually we are close to getting the correct estimate as 27 is very close to 30.

Now assume Jim has 32 sweets, after Jim ate 12, there will be 20 left. Then that means there are 20 x 7 = 140 chocolates.
Ken ate 18 chocolates. That means 122 left. If that is true, then there are 122/4 = 30.5 sweets. Fraction is okay. Actually we are even closer now to getting the correct estimate as 30.5 is very close to 32.

Now assume Jim has 34 sweets, after Jim ate 12, there will be 22 left. Then that means there are 22 x 7 = 154 chocolates.
Ken ate 18 chocolates. That means 136 left. If that is true, then there are 136/4 = 34 sweets. The result is the same as my assumption. So 34 is correct!

But since Jim and Ken each has 34 sweets, so there are 68 sweets total, and 154 x = 308 chocolates.

No need for simultaneous equation. Using this method may be even faster than using simultaneous eqn. Anyone need a PSLE maths tutor?

yea but this methood not much class leh.

 

[night86mare]

And Bill Gates is a school dropout?

and there are also many school dropouts who end up in nameless graves.

it's what you make of life, not all these little things you hang on yourself, whether it's "university graduate" or "baker" or "big shot who drives nice car"..

the happiest person on earth, for all we know, might not even have a house over his head.

if you think bill gates is something, he didn't get there by being a school dropout. he got there by a combination of immeasurable factors.

 

[zaren]

using the dumbed down version of simultaneous equations,

working backwards,

after eating the sweets and chocolates,
jim had J sweets and J J J J J J J chocolates (ratio 1:7)
ken had K sweets and K K K K chocolates (ratio 1:4)

before jim ate 12 sweets and ken ate 18 chocolates,
jim had J+12 sweets and J J J J J J J chocolates
ken had K sweets and K K K K + 18 chocolates

since the sweets and chocolates were shared equally between jim and ken,
sweets: J+12 = K (ratio 1:1)
chocolates: J J J J J J J = K K K K + 18 (ratio 1:1)

replacing K with J+12 in the chocolates equation,

J J J J J J J = J+12 J+12 J+12 J+12 + 18

cancelling J J J J from both sides of the equation,

J J J = 12 + 12 + 12 + 12 + 18
J J J = 66

therefore J = 66/3 = 22.

since K = J+12,
K = 22+12 = 34

before sharing his sweets,
ken bought 2 x K sweets = 2 x 34 = 68 sweets -> answer.

 

[melvin]

I did my PSLE more than 20 years ago, and I think the method that was taught to me still works today. Don't think about algebra or model. Use trial and error. I am not joking.

Try this.

Assume Jim has 20 sweets, after Jim ate 12, there will be 8 left. Then that means Jim has 8 x 7 = 56 chocolates.
Ken ate 18 chocolates. That means 38 left. If that is true, then there are 38/4 = 9.5 sweets. Fraction is okay. Just leave it for the moment. It is to help us to agar-agar the results.

Now assume Jim has 30 sweets, after Jim ate 12, there will be 18 left. Then that means there are 18 x 7 = 126 chocolates.
Ken ate 18 chocolates. That means 108 left. If that is true, then there are 108/4 = 27 sweets. Fraction is okay. Actually we are close to getting the correct estimate as 27 is very close to 30.

Now assume Jim has 32 sweets, after Jim ate 12, there will be 20 left. Then that means there are 20 x 7 = 140 chocolates.
Ken ate 18 chocolates. That means 122 left. If that is true, then there are 122/4 = 30.5 sweets. Fraction is okay. Actually we are even closer now to getting the correct estimate as 30.5 is very close to 32.

Now assume Jim has 34 sweets, after Jim ate 12, there will be 22 left. Then that means there are 22 x 7 = 154 chocolates.
Ken ate 18 chocolates. That means 136 left. If that is true, then there are 136/4 = 34 sweets. The result is the same as my assumption. So 34 is correct!

But since Jim and Ken each has 34 sweets, so there are 68 sweets total, and 154 x = 308 chocolates.

No need for simultaneous equation. Using this method may be even faster than using simultaneous eqn. Anyone need a PSLE maths tutor?

This is much simpler method if the child have patience if he like me sure gone case! As this is one of the method i dun like or i never use then felt it is wasting too much of my time! :bsmilie:

 

[melvin]

using the dumbed down version of simultaneous equations,

working backwards,

after eating the sweets and chocolates,
jim had J sweets and J J J J J J J chocolates (ratio 1:7)
ken had K sweets and K K K K chocolates (ratio 1:4)

before jim ate 12 sweets and ken ate 18 chocolates,
jim had J+12 sweets and J J J J J J J chocolates
ken had K sweets and K K K K + 18 chocolates

since the sweets and chocolates were shared equally between jim and ken,
sweets: J+12 = K (ratio 1:1)
chocolates: J J J J J J J = K K K K + 18 (ratio 1:1)

replacing K with J+12 in the chocolates equation,

J J J J J J J = J+12 J+12 J+12 J+12 + 18

cancelling J J J J from both sides of the equation,

J J J = 12 + 12 + 12 + 12 + 18
J J J = 66

therefore J = 66/3 = 22.

since K = J+12,
K = 22+12 = 34

before sharing his sweets,
ken bought 2 x K sweets = 2 x 34 = 68 sweets -> answer.

:thumbsup: this i finally understand! :embrass: My maths no good!:bsmilie:

 

[zaren]

:thumbsup: this i finally understand! :embrass: My maths no good!:bsmilie:

if you understand, then your maths is ok lah!

if you still don't understand, then we need to find a simpler and clearer explanation of the math solution for you!

actually, maths is not really that difficult, much depends on how well the maths teacher can teach, in a clear, systematic and logical way that all the students can understand.

 

[knpan]

I doubt that primary 6 will know simultaneous equation or algebra, last time , now i do not know the current teaching.
Using Model unit is easier to understand

 

[zaren]

I doubt that primary 6 will know simultaneous equation or algebra, last time , now i do not know the current teaching.
Using Model unit is easier to understand

Anyway, this is my take of the model units method for this problem:

 

[castwind]

This is much simpler method if the child have patience if he like me sure gone case! As this is one of the method i dun like or i never use then felt it is wasting too much of my time! :bsmilie:

Erm... Am not trying to defend my method and it may sound no class, but this can be much faster than using simultaneous equation. I learnt that this is one of the of the best methods to solve abstract questions, use a few assumptions (plug in numbers) to understand the question, then try a few more numbers to get the correct answer. Used this method for many math competitions. It works.

 

[Limsgp]

Ya, the point is, a cert is not everything. In fact, it may be the 1 of the least important factor. Attitude is more important.

if you think bill gates is something, he didn't get there by being a school dropout. he got there by a combination of immeasurable factors.

 

[cheeseme]

Dun believe? It's really that simple. Just draw the model. "S" = 1 part; left hand is Jim || right hand Ken. In RED = eaten

chocolates = S S S S S S S || S 12 S 12 S 12 S 12 18
sweet = S 12 || S 12

Cancel away all the "S" and "12", what's left is

chocolates = S S S || 12 12 12 12 18
so, "S S S" = 12 + 12 + 12 + 12 + 18 = 66. Therefore "S" = 66 / 3 = 22.

Hence, Ken bought S + S + 12 + 12 = 22 + 22 + 12 + 12 = 68 sweets.

Thought I already posted the solution in page 2 and only in a few lines, why is everyone repeating it in various presentation? And seems getting longer and longer...:bsmilie:

Haha, no problem, they just give everyone a better and better understanding to the method use. Which is good for everyone to guide their children, esp those preparing for PSLE next year.

Cheers!

 

[melvin]

Erm... Am not trying to defend my method and it may sound no class, but this can be much faster than using simultaneous equation. I learnt that this is one of the of the best methods to solve abstract questions, use a few assumptions (plug in numbers) to understand the question, then try a few more numbers to get the correct answer. Used this method for many math competitions. It works.

:bsmilie: No problem with ur method bro! Any method is good as long as arrive the ans.
It is just a little troublesome for a lazy guy like me to use this method thats all cos prefer working then ans rather then guessing! :bsmilie:

 

[Benosaurous]

Well, it doesn't matter what you score in PSLE, or A level.

Just got to take note that it is which direction you go after that that counts.

A car salesman makes 8k a month.
A stock broker makes 12k a month
A property agent makes 20k a month.

Go figure that out.

Engineers, accountants, lawyers, doctors make much less than that. This is just a general statement. There are exception, of course.

i have to agree with you, i dont understand why everyone is making each other(their children and their) life so stressful and terrible. Education is a good thing, but excessively just spoil one's interest.

just think of how much ur own education is helping you in your work right now. i feel that most of the time soft skills is more important, the rest can be taught and perfect through time in your work.

i for one, if i have a child, will concentrate more on his soft skills, teaching him the correct values of life and go through education without demanding him anything, than all these moe approved stuff which just grows you into another ministry approved puppet, or even fall into the path of suicide before then.

 

[limdj]

Solving this question only make sure that you are going to be working for ppl instead of being ur own boss.