Q&A - PSLE Math

[MathIzzzFun]

jarenchuatw:

Thanks BB for explaining that time is inversely proportional to speed, given that distance is common. I have definitely learnt something new.


Got another similar question to one that I have asked previously still can't figure out how to do it - due to my lack of imagination. Will need help again for the following question.

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

Thanks

hi

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

28/7 x 9/3 x 66/4 (52) -- cut the 66 cm side into 4 cm each up to 52 cm
= 4 x 3 x 13 blocks = 156 blocks,
leaving a block of 28 cm x 9 cm x 14 cm (66 cm - 52 cm = 14 cm)

The remaining block can be further cut into 28/4 x 9/3 x 14/7 = 7 x 3 x 2= 42 blocks.

total 156 + 42 = 198 blocks

cheers.

[Michaelia0816]

tianzhu:

atutor2001:

[quote]

A man spent 1/5 of his money on clothes and a few sevenths on food. He has $152 left. How much did he spend on food?

This question is actually a prelim question from a neighbourhood school. It is very interesting because it tests the kids understanding of fractions and multiples. For those who love using model, it is the easiest way to understand.

Hi
Is the answer $912?[/quote]Hey, after reviewing question long ago, I got some misunderstooding about this \" amazing\" and \"confusing\" question. I do not understood what do it meant by \" a few sevenths on food\", pls explain and if possible, can I have the model.

[Andrew Lee]

MathIzzzFun:

jarenchuatw:

Thanks BB for explaining that time is inversely proportional to speed, given that distance is common. I have definitely learnt something new.


Got another similar question to one that I have asked previously still can't figure out how to do it - due to my lack of imagination. Will need help again for the following question.

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

Thanks

hi

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

28/7 x 9/3 x 66/4 (52) -- cut the 66 cm side into 4 cm each up to 52 cm
= 4 x 3 x 13 blocks = 156 blocks,
leaving a block of 28 cm x 9 cm x 14 cm (66 cm - 52 cm = 14 cm)

The remaining block can be further cut into 28/4 x 9/3 x 14/7 = 7 x 3 x 2= 42 blocks.

total 156 + 42 = 198 blocks

cheers.

Hello, can help me solve this question, tks
http://i45.tinypic.com/25qgg8n.jpg\">

[Andrew Lee]

MathIzzzFun:

jarenchuatw:

Thanks BB for explaining that time is inversely proportional to speed, given that distance is common. I have definitely learnt something new.


Got another similar question to one that I have asked previously still can't figure out how to do it - due to my lack of imagination. Will need help again for the following question.

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

Thanks

hi

A block of wood 28cm by 66cm by 9 cm was cut into smaller pieces which were 4cm by 7cm by 3cm each. What was the maximum number of pieces that it could be cut into?

28/7 x 9/3 x 66/4 (52) -- cut the 66 cm side into 4 cm each up to 52 cm
= 4 x 3 x 13 blocks = 156 blocks,
leaving a block of 28 cm x 9 cm x 14 cm (66 cm - 52 cm = 14 cm)

The remaining block can be further cut into 28/4 x 9/3 x 14/7 = 7 x 3 x 2= 42 blocks.

total 156 + 42 = 198 blocks

cheers.

Hello, can help me solve this question, \"kum sia\"

http://i46.tinypic.com/aca0e9.jpg\">

[Andrew Lee]

tianzhu:

Shimmer:

Hi Tianzhu

How do you get 1 unit 204 ?

Don't understand this part :

10 units – (6 units + 12) ------ 804

Hi

4 units – 12 ------- 804

4 units ------ 804 + 12 ------ 816

1 unit ------ 816/4 ------- 204

Best wishes

Hello, can help me solve this question

http://i50.tinypic.com/2il1n42.jpg\">

[tianzhu]

Michaelia0816:

Hi Tianzhu, this question is found in my HW, of course, it 462 not 456.
I not sure how to get 144 as my answer? Pls tell how, help me with the (b) part,can?

Hi girl

Good Morning

Hope this helps.

Study hard, eat well, rest well and you are ready for PSLE 2012.

Best wishes

http://farm8.staticflickr.com/7247/7511196950_0b6518d248_z.jpg\">

[tianzhu]

Michaelia0816:

Hey, after reviewing question long ago, I got some misunderstooding about this \" amazing\" and \"confusing\" question. I do not understood what do it meant by \" a few sevenths on food\", pls explain and if possible, can I have the model.

Hi girl

I’ve not much time to draw the MD,so will just give you some pointers.

Draw 5 boxes of similar sizes.

1 box to show money spent on clothes.

Divide the remaining 4 boxes into 7 portions. We’ll have 28 smaller parts.

This means 1 portion is equal to 4 parts.

So we have 4,8,12,16,20,24,28

Find the biggest remaining parts which you can divide 152 with.
In this case, it’s 8.

152/8 ------ 19

Amount spent on food ------ 28-8 ------ 20

20*19 ------ 380

Best wishes

[Shimmer]

Does anyone knows how to solve these two question ?

:thankyou:

Q1 At 9.30am, a car left town X for town Y at a speed of 60km/h for the whole journey. At 11am a lorry started from town Y and travelled towards town X. The speed of the lorry remained the same until it passed the car at 12.30pm. The lorry passed the car at midpoint between town X and town Y and decreased its speed by 20km/h, it travelled at new speed for the rest of the journey. What time did the lorry reach town X ?

Q2 Container A and B are containers with the same square base. Conainer A contains water filled to the brim while container B is empty. After 288cm cubic of water is poured into Container B from Container A, the depth of water in Container B is 60% the depth of water left in container A. What is the length of the square base of Container B ? (Sorry not able to attached the diagram but its show that Container A the height is 48cm)

[tianzhu]

Shimmer:

Does anyone knows how to solve these two question ?

:thankyou:
Q1 At 9.30am, a car left town X for town Y at a speed of 60km/h for the whole journey. At 11am a lorry started from town Y and travelled towards town X. The speed of the lorry remained the same until it passed the car at 12.30pm. The lorry passed the car at midpoint between town X and town Y and decreased its speed by 20km/h, it travelled at new speed for the rest of the journey. What time did the lorry reach town X ?

Hi

For questions on Speed, it’s useful to start with a simple diagram.

9.30am ----- 12.30pm ----- 3h

Car travelled 3*60 ------ 180km

11am ----- 12.30pm ------ 1.5h

Speed of lorry ------ 180/1.5 ------ 120km/h

Lorry’s new speed ------ 100km/h

180/100 ----- 1.8h ------ 1h 48

Hence, the lorry reached Town [email protected]

Best wishes

[Shimmer]

Thanks Tianzhu, you are surperb !!