What if you are stuck in a deserted island.........
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**Stuck on a deserted island even......
You are stuck on a deserted island (A), there are 2 other islands (B) and (C). You know the distance from island (A) to (B) is 90km and island (B) to (C) is 40km. You plan to sail from island (A) to (C) and you wish to know the distance in order to plan your journey. Island A-B-C makes a right angle triangle. (You do not have a calculator with you).
What is the distance from island (A) to (C)?
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98.5km or 80.62km?
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ah...40^2 + 90^2 = 1600+8100 = 9700 So, sqrt 9700 = sqrt(25x388 ) = 5sqrt(388 ) Can just leave the answer in sqrt form?
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Originally posted by la luce nella piazza:
98.5km or 80.62km?
You are on a deserted island, like on survivor, you do no have a calculator.
Please explain how you derive your answer?
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C
4
0
A 90 B
By Pythagoras' theorm since it is a right-angled triangle:
AC² = AB² + BC²
AC² = 40² + 90²
AC² = 1600 + 8100
AC² = 9700
AC = sqrt9700
AC = wtf
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Yes yes. I know it's square root of 9700, but then you do not have a calculator.
What is the answer to 2 decimal places?
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Originally posted by deepak.c:
Yes yes. I know it's square root of 9700, but then you do not have a calculator.
What is the answer to 2 decimal places?
Mental calculations cannot have decimals meh?
Maybe the guy is smarter than you?
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Originally posted by charlize:
Mental calculations cannot have decimals meh?
Maybe the guy is smarter than you?
Mental calculations can have decimals.
The guy is definitely smarter than me.
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A smart guy would take the calculator along and save himself all these trouble.
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just use your traditional long division method lah, you are suppose to use this to test your long division good or not mah.
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Is this a trick question?
You say stuck on an island and then you say that I can sail to another island.
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Originally posted by deepak.c:
You are on a deserted island, like on survivor, you do no have a calculator.
Please explain how you derive your answer?
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Use the theory of a^2 - b^2 = (a+b)(a-b)
99^2 = 99 x 100 - 99 = 9801
98^2 = 98 x 100 - 98 x 2 = 9604
Consider 98.5^2
99^2 - 98.5^2 = 0.5 x (99 + 98.5) = 98.75
=> 98.5^2 = 9801 - 98.75 = 9801 - 100 + 1.25 = 9702.25
98.5^2 > 9700.
Consider 98.49^2.
98.5^2 - 98.49^2 = (98.5 + 98.49) (0.01) = 1.9699
=> 98.49^2 = 9702.25 - 1.9699 = 9702.25 - 2 + 0.0301= 9700.2801
Given that difference between 98.48^2 and 98.49^2 will be >> 0.2801 (by deduction by observing 98.5^2 - 98.49^2),
HENCE distance AC is 98.49km (to 2 d.p)
on the other hand, he's on a deserted island already, so if he bother to do this stupid thing he should probably stay there.
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Originally posted by charlize:
Is this a trick question?
You say stuck on an island and then you say that I can sail to another island.
and wtf would i need to know the distance?
it ain't going to be a big help
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Originally posted by charlize:
Is this a trick question?
You say stuck on an island and then you say that I can sail to another island.
LOL! Nice... -
Originally posted by SBS261P:
on the other hand, he's on a deserted island already, so if he bother to do this stupid thing he should probably stay there.
Deepak is that man. He is asking us through wireless labby how to get off the island. He is using coconuts to charge his labby. XD
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Originally posted by Daisuke-kun:
and wtf would i need to know the distance?
it ain't going to be a big help
LOL
i wouldnt care the disntace, just swim la. -
Originally posted by maskedangel:
LOL
i wouldnt care the disntace, just swim la.i cannot swim so it won't make any difference as well
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Originally posted by maskedangel:
LOL
i wouldnt care the disntace, just swim la.90+km You will die before you finish it.
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Originally posted by SBS261P:
Use the theory of a^2 - b^2 = (a+b)(a-b)
99^2 = 99 x 100 - 99 = 9801
98^2 = 98 x 100 - 98 x 2 = 9604
Consider 98.5^2
99^2 - 98.5^2 = 0.5 x (99 + 98.5) = 98.75
=> 98.5^2 = 9801 - 98.75 = 9801 - 100 + 1.25 = 9702.25
98.5^2 > 9700.
Consider 98.49^2.
98.5^2 - 98.49^2 = (98.5 + 98.49) (0.01) = 1.9699
=> 98.49^2 = 9702.25 - 1.9699 = 9702.25 - 2 + 0.0301= 9700.2801
Given that difference between 98.48^2 and 98.49^2 will be >> 0.2801 (by deduction by observing 98.5^2 - 98.49^2),
HENCE distance AC is 98.49km (to 2 d.p)
on the other hand, he's on a deserted island already, so if he bother to do this stupid thing he should probably stay there.
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.
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tt's a neat way of looking at it... sorry la rusty le, NS leh.
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nt equal is approximate to. paiseh
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Since you cannot use calculator and you obviously cannot square root 9700 mentally,
I think the best way is to draw out a scaled drawing of your island formation using a ruler and pencil on a piece of paper.
using a suitable scale, (I would use 10km: 1cm)
draw your right angle triangle. labeling your island at each point of the triangle.. A,B,C
Now use you ruler and measure how long is A to C.
You will get your answer just by converting the measurement of A to C with the scale you used =)
simple??
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Originally posted by Lt Viper:
Since you cannot use calculator and you obviously cannot square root 9700 mentally,
I think the best way is to draw out a scaled drawing of your island formation using a ruler and pencil on a piece of paper.
using a suitable scale, (I would use 10km: 1cm)
draw your right angle triangle. labeling your island at each point of the triangle.. A,B,C
Now use you ruler and measure how long is A to C.
You will get your answer just by converting the measurement of A to C with the scale you used =)
simple??
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.
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Originally posted by Forbiddensinner:
90+km You will die before you finish it.
spartans can do it!
oh weel, like daisuke say, don bother lor. .