PSLE Maths question. How to solve?

[Rayleigh]

Probably like this

 

unshaded A = 1/4

unshaded B = 3/12 = 1/4

total unshaded =1/4

 

Untitled.jpg

 

 

Thank you very very much. Sometimes, we really think too chim.

[Kb27]

Probably like this

 

unshaded A = 1/4

unshaded B = 3/12 = 1/4

total unshaded =1/4

 

Untitled.jpg

 

Shouldn't the total unshaded A+B = 1/4 + 1/4 = 1/2 ?

[Darryn]

Hi All

 

Anyone knows how to solve this P6 math question?

Was it multi guess or long answer?

[Ender]

Thank you very very much. Sometimes, we really think too chim.

Yah, think too much...

[Rayleigh]

Shouldn't the total unshaded A+B = 1/4 + 1/4 = 1/2 ?

 

No it shouldnt be cos it is not summation but proportional. For example, Item A given 20% discount and Item B given 20% discount, the net discount is still 20% off the combine cost. 

[Kb27]

No it shouldnt be cos it is not summation but proportional. For example, Item A given 20% discount and Item B given 20% discount, the net discount is still 20% off the combine cost. 

 

Ha, I would fail psle maths nowadays.

[1fast1]

Shouldn't the total unshaded A+B = 1/4 + 1/4 = 1/2 ?

 

No. It's bad practice to reuse A and B for the areas since those are already defined in the question. So let's use x for the area of the biconvex (eye of Sauron/cat's pupil) shape and y for the smaller area.

 

Unshaded area = 3y + x

 

Total area = 12y + 4x = 4(3y + x)

 

So unshaded area = 1/4 of the total.

[Hiphiphoray]

Dear psle maths gurus.

 

Pls help contribute the answer.....hehehe.

[Ender]

Dear psle maths gurus.

 

Pls help contribute the answer.....hehehe.

The shaded area has the same area as the 9 x 5 trapezium.

Reason is since both triangles are identical and have the same overlapping area. So the "non-overlapped" area are the same for both triangle.

 

Just apply the trapezium formula for area, or for p6, will be split the trapezium into a 6 x 5 rectangle and a 3 x 5 triangle and add them up

Edited August 12, 2016 by Ender

[Hiphiphoray]

The shaded area has the same area as the 9 x 5 trapezium. Reason is since both triangles are identical and have the same overlapping area. So the "non-overlapped" area are the same for both triangle.

 

Just apply the trapezium formula for area, or for p6, will be split the trapezium into a 6 x 5 rectangle and a 3 x 5 triangle and add them up

You are the man!!!

[Topspin]

The shaded area has the same area as the 9 x 5 trapezium.

Reason is since both triangles are identical and have the same overlapping area. So the "non-overlapped" area are the same for both triangle.

 

Just apply the trapezium formula for area, or for p6, will be split the trapezium into a 6 x 5 rectangle and a 3 x 5 triangle and add them up

 

Clap clap

[Wind30]

by proportion it is easy to calculate the overlap area too. Then  just minus 

[Hiphiphoray]

Can I treat it as 1 unshaded triangle = 1/2 x 5 x 3 = 7.5.

 

The other 5 shaded triangle is equally identical so 7.5 x 5 = 37.5 cm2

 

Like this ok? But im not comfortable doing this way bcos I totally skip making use of 9cm.

 

How do you make use of all 9cm 3cm 5cm information and solve it using rect + tri combination?

 

The shaded area has the same area as the 9 x 5 trapezium.

Reason is since both triangles are identical and have the same overlapping area. So the "non-overlapped" area are the same for both triangle.

 

Just apply the trapezium formula for area, or for p6, will be split the trapezium into a 6 x 5 rectangle and a 3 x 5 triangle and add them up

Edited August 12, 2016 by Hiphiphoray

[Ender]

Can I treat it as 1 unshaded triangle = 1/2 x 5 x 3 = 7.5.

 

The other 5 shaded triangle is equally identical so 7.5 x 5 = 37.5 cm2

 

Like this ok? But im not comfortable doing this way bcos I totally skip making use of 9cm.

 

How do you make use of all 9cm 3cm 5cm information and solve it using rect + tri combination?

 

Yes, you can treat is as 5 little triangles.

 

But what I would do is recognised that the trapezium on the right is exactly the same area as the shaded area as explained earlier.

 

The  trapezium formula = (9+6)/2 X 5 = 37.5 cm2

Edited August 12, 2016 by Ender

[Hiphiphoray]

PSLE Maths 2018 Q 28 (2 marks) - actual question

 

Can somebody help me to answer this question...….in as simpler form as possible suitable for a 12 year old kid to absorb.

 

Thank you.

 

Jasmin formed two cuboids with unit cubes.

The length, breadth and height of the bigger cuboid are 2 times those of the smaller cuboid.

She used 384 unit cubes to form the bigger cuboid.

 

How many unit cubes did she use to form the smaller cuboid?

 

I got the answer by trial & error via the factors of 384. Wonder if there is a simpler answer.

 

PS....I personally feel that the actual PSLE Maths Exam is a lot easier than the SA2 paper of some schools....(namely Nan Hua, Rosyth, Raffles....they set unbelievable difficult questions!! Put unnecessary stress on students.)

[Ender]

Visualise by stacking cubes. Use match boxes. The bigger cuboid whose length, breath and height is twice the smaller will be 8 times bigger in volume.. 384/8 =48?

[Hiphiphoray]

hmmm...make sense.

 

2U : 1U  --> 4x4x4  : 2x2x2

=

64 : 8 ( 8 times bigger)

 

hence 348/8 = 48.

 

U are really good in P6 Maths. Thanks.

[1fast1]

PSLE Maths 2018 Q 28 (2 marks) - actual question

 

Can somebody help me to answer this question...â¦.in as simpler form as possible suitable for a 12 year old kid to absorb.

 

Thank you.

 

Jasmin formed two cuboids with unit cubes.

The length, breadth and height of the bigger cuboid are 2 times those of the smaller cuboid.

She used 384 unit cubes to form the bigger cuboid.

 

How many unit cubes did she use to form the smaller cuboid?

 

I got the answer by trial & error via the factors of 384. Wonder if there is a simpler answer.

 

PS....I personally feel that the actual PSLE Maths Exam is a lot easier than the SA2 paper of some schools....(namely Nan Hua, Rosyth, Raffles....they set unbelievable difficult questions!! Put unnecessary stress on students.)

This is a similarity question asked before they've learned about similarity (Secondary subject). Volume ratios are the cube of the side ratios.

 

Anyway they've done basic algebra in P6, so just say that small cuboid volume is xyz but large cuboid volume is (2x)(2y)(2z)=(2)(2)(2)xyz = 8xyz. That's how you get eight times lol.