I'm ashamed of the maths standard in Singapore....
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I don't know if I shall be more inspired in joining MOE or stay away from them....
Question: Find the area of rectangle C.
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gee....err....i dunno..
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*tries to act smart*
Issit 22cm square? *craoks* -
what is the problem? just flick the big triangle over to get a bigger triangleOriginally posted by CoolMyth:I don't know if I shall be more inspired in joining MOE or stay away from them.... -
1/2 x 15 x 6 = X
then minus off 16 cm 2 and 4 cm 2
X - 16 cm 2 - 4 cm 2 = 25 cm 2
so easy lor
the answer is 25 cm 2
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obviouslyOriginally posted by DriftingGuy:what is the problem? just flick the big triangle over to get a bigger triangle -
let the side of rect c be x and y.
area of c = x*y = 45-4-16=25
area of a = 1/2*(15-x)*y=4
area of b = area of flipped triangle = 1/2*x*(6-y)=16
Since triangle a and b touches each other, the above 3 equation must all be satisfied for one set of x and y. And that's quite hard to get, if any.
Another way of looking at this question is to look at the simultaneous equation 2 and 3, solve for x and y. and aha you realise x*y not equal 25cm2 -
kaoz looks like primary skool question but its simultaneous eqn leh
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Originally posted by DriftingGuy:what is the problem? just flick the big triangle over to get a bigger triangle
Actually, I didn't know being a teacher is so easy also....
Anyhow set question also can.... -
I think some information was omitted from the test paper... e.g. the diagram itselfOriginally posted by CoolMyth:
Actually, I didn't know being a teacher is so easy also....
Anyhow set question also can.... -
It's just inconsistency lah:
Method 1:
Flip B over:
Hence, area of big triangle = 1/2 * 90 = 45
Area of C = 45 - 16 - 4 = 25cm^2
Method 2:
Ratio:
Since area of triangles A and B is in the ratio 1:4 --> their lengths is in the ratio 1:2
Hence, consider shortest side of triangle A = 1/3 * 6 = 2
Therefore, second shortest side of A = (4*2)/2 = 4 (Manipulate triangle area formula)
--> Longer side of rectangle C = 15 - 4 = 11
--> Area of C = 11 x 2 = 22cm^2
25 not equal to 22!
MOE shall consider giving extra marks to students who write both methods and ended it with "MOE xia suay, LOL!" -
Method 3:
Consider second shortest side of triangle B
--> Length = 2/3 * 15 = 10
Length of shortest side of A = 2
Hence, area of C = 10 x 2 = 20!
20, 22, 25, eh, I need another three more numbers for Toto leh! -
wah.. so hard ar?? mi dunno how to do leh.. mi more ashamed of my math standard ar
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Looks like coolmyth the maths whiz is back.. -
...Originally posted by CoolMyth:It's just inconsistency lah:
Method 1:
Flip B over:
Hence, area of big triangle = 1/2 * 90 = 45
Area of C = 45 - 16 - 4 = 25cm^2
Method 2:
Ratio:
Since area of triangles A and B is in the ratio 1:4 --> their lengths is in the ratio 1:2
Hence, consider shortest side of triangle A = 1/3 * 6 = 2
Therefore, second shortest side of A = (4*2)/2 = 4 (Manipulate triangle area formula)
--> Longer side of rectangle C = 15 - 4 = 11
--> Area of C = 11 x 2 = 22cm^2
25 not equal to 22!
MOE shall consider giving extra marks to students who write both methods and ended it with "MOE xia suay, LOL!" -
Actually, I prefer method 3.. cos it uses hard figures instead of eye power to calculate the area.. this is in case they argue that the flip side of triangle B is not really a same size triangle
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Cannot use method 2. Triangles not similar.
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Actually I also have a maths question.. I normally have experience solving maths questions in sec and pri school level since my house has tuition kids.. but this one really really stumped me... I wonder if anyone here can help me solve? -
That Maths Qn, is going to be a laughing stock
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Is it? He is assuming that the diagonal of A and B forms a straight line.. If the diagonal is assumed straight then they are similar right?Originally posted by shade343:Cannot use method 2. Triangles not similar. -
[quote]Originally posted by HyuugaNeji:
[b]
Nice try...didnt catch you first time. -
Seriously, you cannot assume if you set the qn...Originally posted by DriftingGuy:Is it? He is assuming that the diagonal of A and B forms a straight line.. If the diagonal is assumed straight then they are similar right?
And usually, such qn, there is no way to solve because of the diagonal length -
eh if you dont assume those are similar triangles, you also cannot assume you can flip triangle b meaning the middle line is not horizontal. (parallel to the base line)
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The diagonal across the rectangle is supposed to join the two triangles together.Originally posted by shade343:Cannot use method 2. Triangles not similar.
Of course, I'm not looking at the lengths and stuff.
Some foreign newspapers shall pick up this news and "praise" Singapore for having such a world-class education. -
All they have to do is include a footnote "diagonal of A and B forms a straight line"Originally posted by sbst275:Seriously, you cannot assume if you set the qn...
And usually, such qn, there is no way to solve because of the diagonal length
But then again this is an mcq question..