Q&A - PSLE Math

[tianzhu]

Spongy:

2. Marvin and Nick had some twenty-cent coins each. If Marvin gave 1/3 of his share to Nick, Nick would have 210 coins more than Marvin. If Marvin gave 1/4 of his share to Nick, the ratio of number of Marvin's coins to the number of Nick's coins would become 3:7. What is the difference between the sum of money that each of them had?

Hi

Case 1

In the end

Marvin ------ 8 units
Nick ------ 8 units + 210

At first

Marvin ------ 12 units
Nick ------ 4 units + 210

Case 2

In the end

Marvin ------ 9 units
Nick ------ 7 units + 210

9 units : 7 units + 210 ------- 3:7

Cross multiply

63 units ------- 21 units + 630

42 units ------ 630

1 unit ------ 15

Marvin ------ 12 unit ------ 180

Nick ------ 4 units + 210 ------ 270

Difference ------- 90

Best wishes

[tianzhu]

Shimmer:

May I know according to the model it's show the ten dollar x 2 which is 8 units but I thought its should be 1.5 times ? Thanks to advise. Greatly appreciate.

Hi

The first set of MD shows number while the second set of MD shows value.

Best wishes

[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

[tianzhu]

Spongy:

1. 1/4 of the marbles in a box are red and the rest are either blue or green. If there are 36 more blue than twice the number of green ones, how many more red marbles than green marbles a there?

Hi

Green ------ 1 unit

Blue ------ 2 units + 36

3 units + 36 ------ 3 parts (3/4)

1 unit + 12 ------ 1 part (1/4)

Red ------ 1 unit + 12

Hence there are 12 more red marbles than green marbles.

Best wishes

[Shimmer]

tianzhu:

Shimmer:

Hi all


One more question.

Ravi put some eggs into 3 boxes box A, box B and box C. 1/2 of the eggs in box A is equal to 3/10 of the eggs in box B . The numbers of egg in box C is 16 more than 1/2 of the total numbers of eggs in box A and box B, if 25% of the eggs in box C were broken and removed, there were 804 more eggs in box B than in box C. Ravi sold each egg at 8 cents. How much did he earn ?

Hi

Box A ----- 6 units

Box B ------ 10 units

Box C ----- 8 units + 16

25% of the eggs in box C were broken and removed.

Box C (removed) ----- 2 units + 4

Box C (left) ----- 6 units + 12

There were 804 more eggs in box B than in box C.

10 units – (6 units + 12) ------ 804

1 unit ----- 204

Number of eggs sold ------ 22 units + 12 ------ 4500

Ravi sold each egg at 8 cents

4500*8 ------ $360.

Best wishes

Hi Tianzhu

How do you get 1 unit 204 ?

Don't understand this part :

10 units – (6 units + 12) ------ 804

[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

[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\">