What if you are stuck in a deserted island.........
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Originally posted by deepak.c:
Can do multiplication along the beach, you have miles and miles of fine sand. Unless you can't do simple multiplication, then you won't know the distance liao.
98
x98
784
882
9,604
** I forgot to mention no rulers also.
but tedious leh..........actually sand can also do long division of up to 10 degrees functions.....
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Originally posted by SBS n SMRT:
but tedious leh..........actually sand can also do long division of up to 10 degrees functions.....
Maybe that's one method, but for me, I hate doing division, I'd rather do multiplication.
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Originally posted by Forbiddensinner:
90+km You will die before you finish it.
the boat might have motor!! ... -
Originally posted by deepak.c:
Can do multiplication along the beach, you have miles and miles of fine sand. Unless you can't do simple multiplication, then you won't know the distance liao.
98
x98
784
882
9,604
** I forgot to mention no rulers also.
You don't need to have a ruler. All you need is something you can fold five time into 10 parts. Let that particular length represent10km. Each part will be 1km. Do the diagram on the fine sand.
If you don't have the equipment or ability to do this, then you don't have the ability to sail either. :) -
Originally posted by Mikethm:
You don't need to have a ruler. All you need is something you can fold five time into 10 parts. Let that particular length represent10km. Each part will be 1km. Do the diagram on the fine sand.
If you don't have the equipment or ability to do this, then you don't have the ability to sail either. :)How do you produce the 90 degree angle?
How do you intrepret 0.49?
What if it's 0.13?
Make 100 folds on the banana leaf?
You don't need complicated equipment to make a raft, you just need to find some vines to tie the pieces of logs together and make some form of sail or paddle.
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Originally posted by SBS n SMRT:
but tedious leh..........actually sand can also do long division of up to 10 degrees functions.....
when the wind blow then hong gan -
Originally posted by deepak.c:
How do you produce the 90 degree angle?
How do you intrepret 0.49?
What if it's 0.13?
Make 100 folds on the banana leaf?
You don't need complicated equipment to make a raft, you just need to find some vines to tie the pieces of logs together and make some form of sail or paddle.
But but YOU learnt how to produce the 90 degree angle in Elementary Maths in Sec School... All you need is a Y shaped twig.
Draw a straight line in the sand. Hold one end of the twig on a point. CUT in semi circle. Go to another point on the line. CUT CUT. THERE. You got the perpendicular bisector between the 2 points which happens to be 90 degree.
And you need to measure to decimal places in preparation for a journey on a raft made of vines and logs???
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Originally posted by Mikethm:
But but YOU learnt how to produce the 90 degree angle in Elementary Maths in Sec School... All you need is a Y shaped twig.
Draw a straight line in the sand. Hold one end of the twig on a point. CUT in semi circle. Go to another point on the line. CUT CUT. THERE. You got the perpendicular bisector between the 2 points which happens to be 90 degree.
And you need to measure to decimal places in preparation for a journey on a raft made of vines and logs???
You'd rather do all these than my method?
I post again below for your perusal.
How do you measure 0.49?
f (x) = x^(1/2)
f (x + delta x) = f (x) + f' (x) dx
= sqrt (9,604) + [1 /2 (9,604)^(0.5)] * (96)
= 98 + 0.489
= 98.49 km (approximation)
** dx = (9,700 - 9604)
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Originally posted by deepak.c:
You'd rather do all these than my method?
How do you measure 0.49?
I would rather use whatever method which occur to the person at the moment. It occur to the other guy who thought of scale drawing to do this... and it is perfectly feasible for the task at hand.
I don't see why we need to measure to the decimal place. Perhaps if I tell you I had canoed around Singapore as in spent 3 days on a round trip... you will concede that I know better than you that decimals does not matter in the task at hand.
Different people have different way of solving problems. For example, I would like you to find the radius of the circle in the following diagram.
Triangle ABC is right angled.AC, AB and BC are tangents to the circle. AC = 13cm and AB = 5cm.
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Originally posted by Mikethm:
I would rather use whatever method which occur to the person at the moment. It occur to the other guy who thought of scale drawing to do this... and it is perfectly feasible for the task at hand.
I don't see why we need to measure to the decimal place. Perhaps if I tell you I had canoed around Singapore as in spent 3 days on a round trip... you will concede that I know better than you that decimals does not matter in the task at hand.
Different people have different way of solving problems. For example, I would like you to find the radius of the circle in the following diagram.
AC, AB and BC are tangents to the circle. AC = 13cm and AB = 5cm.
Ok.
Your preference is to draw a scale.
You are correct.
Happy.
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When you sail out to sea, i think it will be very difficult to keep track on how many kms you already covered.
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Oh by the way, I can sail the topper and laser classes and operate a motor boat. And I tell you that decimals does not matter. :P
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Originally posted by HyuugaNeji:
When you sail out to sea, i think it will be very difficult to keep track on how many kms you already covered.
It is impossible due to relative velocity and currents. -
Originally posted by Mikethm:
Oh by the way, I can sail the topper and laser classes and operate a motor boat. And I tell you that decimals does not matter. :P
I am sure it doesn't matter, but the question required 2 decimal places. Maybe you can state your exam answer as 98 km when your question asked for 2 decimal places.
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u're on a deserted island leh
how the hell do u know the distances are 90 and 40km respectively?
and how do u even see the islands?
u know how far anot?
u got special eyes?
so this question is invalid.
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Originally posted by deepak.c:
Anyway I was just trying to make things interesting for maths students.
Your answer abit tedious.
f (x) = x^(1/2)
f (x + delta x) = f (x) + f' (x) dx
= sqrt (9,604) + [1 /2 (9,604)^(0.5)] * (96)
= 98 + 0.489
= 98.49 km (approximation)
** dx = (9,700 - 9604)
Short and sweet, but you are probably much smarter than me because you ridicule me.
Think I shouldn't contribute because folks here are nasty. Should just keep everything to myself.
That is the problem of Maths education in our country.
Primary 6 students can use calculator now.
They are not taught how to find square root of a value manually.
To find square root of 9700.
1. 99 x 99 = 9801
2. 98 x 98 = 9604
3. Hence, an estimate value of square root of 9700 is 98.5 km.
Short-cut to calculate 98 x 98 = 9604
2 2 04
96 96
Short-cut to calculate 99 x 99 = 9801
1 1 01
98 98
Another example short cut to calculate 98 x 93 = 9114
2 7 14
91 91
Alternatively, google it
http://www.bbc.co.uk/dna/h2g2/A827453
http://math.arizona.edu/~kerl/doc/square-root.html
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Originally posted by Mikethm:
It is impossible due to relative velocity and currents.You sail?
Wind is irrelevant too?
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Originally posted by deepak.c:
I am sure it doesn't matter, but the question required 2 decimal places. Maybe you can state your exam answer as 98 km when your question asked for 2 decimal places.
I am a practical person. If you have said it was an exam question and state which exams it is and the required accuracy... I will give you the appropriate answer. I answer my students' questions by which level and which topics they are doing.If your question was meant as a mathematical test instead of a mental exercise, you would have a point. However, as you can see, most of us took it as a mental exercise. So perhaps the blame lies on you for being unclear as to the intent of your question?
Come on, answer the question I posted to the requirement of O level Elementary Mathematics.
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Originally posted by deepak.c:
You sail?
Wind is irrelevant too?
Wind affect relative velocity. I did mentioned relative velocity. -
(5-r) + (12-r) =13
17 - 2r = 13
r = 2
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Originally posted by ChoCoChips:
u're on a deserted island leh
how the hell do u know the distances are 90 and 40km respectively?
and how do u even see the islands?
u know how far anot?
u got special eyes?
so this question is invalid.
Ok.
Noted.
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Originally posted by Mikethm:
Wind affect relative velocity. I did mentioned relative velocity.Relative velocity is also affected by current, density and temperature of water leh. Don't forget coriolis effect also.
If you fly a plane in a North South orientation for 2 hours, you would have missed your destination by 30 degrees.
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Originally posted by HyuugaNeji:
(5-r) + (12-r) =13
17 - 2r = 13
r = 2
correct.
The elegant answer.
However, some people will go find angle BAC.
Divide it into 2 (where this value is x).
than use r/3= tan x
and get an answer which is 2.00 (not exact) due to rounding error.
Would it be fair for the marker to say these people are wrong just because the elegant answer is exact?
The point of my posted question is to point out that different people have different way of doing things. And unless you state the condition ( EXACT ANSWER) right at the start, then you do not have the right to say that the person's solution is wrong if it is valid in the spirit of the question.
This is a very important issue to me. So much so that I am willing to sacrifice effeciency so that my students can do things the way they prefer. Unless their default method is <90% consistent, I just will bear with it even if forcing them to switch to my way will improve their marks by a bit. Creative thinking is very important.
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Originally posted by Mikethm:
correct.
The elegant answer.
However, some people will go find angle BAC.
Divide it into 2 (where this value is x).
than use r/3= tan x
and get an answer which is 2.00 (not exact) due to rounding error.
Would it be fair for the marker to say these people are wrong just because the elegant answer is exact?
The point of my posted question is to point out that different people have different way of doing things. And unless you state the condition ( EXACT ANSWER) right at the start, then you do not have the right to say that the person's solution is wrong if it is valid in the spirit of the question.
This is a very important issue to me. So much so that I am willing to sacrifice effeciency so that my students can do things the way they prefer. Unless their default method is <90% consistent, I just will bear with it even if forcing them to switch to my way will improve their marks by a bit. Creative thinking is very important.
FYI, on my No.6 post I did mention that it be stated to 2 decimal places, something which I have omitted in my original post.
I have done my practical calculation showing you the results.
You have yet to present to me your results without the aid of a ruler or a calculator, perhaps you could have the courtesy of showing how your method can be done accurately, with minimal errors in measurement using twigs, sand and folding leaves perhaps.
Like I said before, your method is cumbersome and inaccurate to be practical.
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Hi,
Nothing mathematical for me. I'll look out for clean water sources and reflective materials to save myself from dying first :P
Cheers,
Wen Shih