Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

cafelatte:

Thank you, Bobby163.


Thank you, mathsguru. Your model is very clear and easy to understand. Goodness, you made it look so simple ! :oops: Thanks again !!

Hi Cafelatte,

Glad you understood it. Try drawing a model out the next time you/your child encounter such questions. You may not get the model right the first time and may need to modify here and there as you \"pile\" more information into the model, but it's ok. Take it as a rough sketch. The more you practise, the better you can visualise what kind of model you need. :rahrah:

Haha...to be honest, it was so much faster to solve this using paper and pen. I spent like a good 30 minutes drawing using comp... *sweat sweat*
:faint: Need to invest in some model drawing software if I do this full time...keke

~MathsGuru~

[James Ang]

Vikaesh:

Please help me solve the following Question.

The answer is 9 [I saw answer key] but i do not know how to derive at it. Please help me. Thank you!


http://www.postimage.org/image.php?v=aVWRlpi

answer is 9. because all the numbers are 1.

1+1+1+1+1+1+1+1+1 = 9

This is just a common sense question because if you add them together 1^2+2^2+3^2 +.... 8^2+9^2 = 285

QED

[mathsguru]

Vikaesh:

Please help me solve the following Question.

The answer is 9 [I saw answer key] but i do not know how to derive at it. Please help me. Thank you!
http://www.postimage.org/image.php?v=aVWRlpi

Hi Vikaesh,

In my opinion, this question is a little beyond the usual Primary School syllabus. May I know which level is this question from?

Regardless, here's my solution & explanation. Hope it helps!

http://www.postimage.org/image.php?v=Ts1PmD0i

Cheers,
MathsGuru

[cafelatte]

mathsguru, glad to hear that ! Honestly, my eyes and brains are crossed from reading the question and answer !


Vikaesh, I am also keen to know which level the question is for ?

[david59]

My GEP student who had just left my centre after his PSLE, shown me this kind of questions from his maths homework. Once a while, Pri 6 students are given such kind of questions just to amuse them only. [/b]

[mathsguru]

Vikaesh:

Thanks for the solution mathsguru, BTW this is a Maths Olympiad Qn!

You're most welcome Vikaesh! And yeap...I thought so too...should be an Olympiad question.

[mathsguru]

Vikaesh:

Here's another one:

1/a + 1/b + 1/c = 57/58
What is the smallest possible sum of a+b+c

Hi Vikaesh,

Here's my solution. However, since the question does not say much of the numbers a, b and c, I made my own assumptions and obtained 2 answers for the 2 sets of assumptions. :lol:

http://www.postimage.org/image.php?v=Pq1gPFi9
Curious to know what the answer key says though... :?

Regards,
MathsGuru

[fudgemum]

The question is


Given that the value of the sum 1/a + 1/b + 1/c lies between 28/29 and 1, find the smallest possible value of a+b+c where a, b and c are whole numbers.

The answer for this question is 12. This is SMOPS 2009 first round question.

I tried using guess and check method starting with 1. 1 is not possible because the result will be more than 1. 2 and 3 are possible.
1/2 + 1/3 = 0.8333.
The other number cannot be 4 and 5. The sum will be more than 1. If it is 6, the sum will be exactly 1. So it should be 7.
1/2 +1/3 + 1/7 is less than 1 and greater than 28/29.

So the answer is 2+3+7 = 12.

[mathsguru]

fudgemum:

The question is


Given that the value of the sum 1/a + 1/b + 1/c lies between 28/29 and 1, find the smallest possible value of a+b+c where a, b and c are whole numbers.

The answer for this question is 12. This is SMOPS 2009 first round question.

I tried using guess and check method starting with 1. 1 is not possible because the result will be more than 1. 2 and 3 are possible.
1/2 + 1/3 = 0.8333.
The other number cannot be 4 and 5. The sum will be more than 1. If it is 6, the sum will be exactly 1. So it should be 7.
1/2 +1/3 + 1/7 is less than 1 and greater than 28/29.

So the answer is 2+3+7 = 12.

Hi Fudgemum,

Thanks for clarifying!! No wonder no matter how I solve, I can't seem to get the answer \"12 based on Vikaesh's original question...

Hi Vikaesh >> Is Fudgemum's question correct?

Regards,
MathsGuru

[david59]

fudgemum:

The question is


Given that the value of the sum 1/a + 1/b + 1/c lies between 28/29 and 1, find the smallest possible value of a+b+c where a, b and c are whole numbers.

The answer for this question is 12. This is SMOPS 2009 first round question.

I tried using guess and check method starting with 1. 1 is not possible because the result will be more than 1. 2 and 3 are possible.
1/2 + 1/3 = 0.8333.
The other number cannot be 4 and 5. The sum will be more than 1. If it is 6, the sum will be exactly 1. So it should be 7.
1/2 +1/3 + 1/7 is less than 1 and greater than 28/29.

So the answer is 2+3+7 = 12.

While I understand your rationale of 1/2 +1/3 + 1/7 is less than 1 and greater than 28/29, the total sum of the three is equal to 41/42 = 0.97619
but the value of 57/58 is 0.98275.
Since the question states that the value of the three is equal to 57/58, how then is the answer 2, 3 n 7 correct when they do not give the same equal value.
Sorry, pardon my ignorance. I would like to learn. :?