Q&A - PSLE Math

[susutoo]

MathIzzzFun:

susutoo:

http://i49.tinypic.com/aoxq3b.jpg\">

Another Q, pls help

Hi

http://postimage.org/image/gyciubnm
cheers.

Thank you
:salute:

[susutoo]

MathIzzzFun:

susutoo:

Please help

1) There are more pens in box A than box B. 30% of the pens in box A is 60 more than 40% of the pens in box B. If 5% of the pens in box A is transfered to box B, there will be 300 more pens in box A than box B.
a) How many pens are there in box B?
b) How many percentage less pens are there in box B than box A?

Hi

40% of Box B --> 12 units ---- Box B --> 30 units
30% of A --> 12 units + 60 ----- Box A --> 40 units + 200
5% of Box A --> 2 units + 10
After transfer:

Box B --> 32 units + 10
Box A --> 38 units + 190
So, 38 units + 190 = 32 units + 10 + 300
1 unit --> 20

Box B --> 30 x 20 = 600 pens
Box A --> 40 x 20 + 200 = 1000 pens
(1000-600)/1000 x 1
00% = 40%
There are 40% less pens in Box B than in Box A.

cheers.

Thank you!

Can you explain how to get 12 units for 40% of box B.

[MathIzzzFun]

susutoo:

MathIzzzFun:

[quote=\"susutoo\"]Please help

1) There are more pens in box A than box B. 30% of the pens in box A is 60 more than 40% of the pens in box B. If 5% of the pens in box A is transfered to box B, there will be 300 more pens in box A than box B.
a) How many pens are there in box B?
b) How many percentage less pens are there in box B than box A?

Hi

40% of Box B --> 12 units ---- Box B --> 30 units
30% of A --> 12 units + 60 ----- Box A --> 40 units + 200
5% of Box A --> 2 units + 10
After transfer:

Box B --> 32 units + 10
Box A --> 38 units + 190
So, 38 units + 190 = 32 units + 10 + 300
1 unit --> 20

Box B --> 30 x 20 = 600 pens
Box A --> 40 x 20 + 200 = 1000 pens
(1000-600)/1000 x 1
00% = 40%
There are 40% less pens in Box B than in Box A.

cheers.

Thank you!

Can you explain how to get 12 units for 40% of box B.[/quote]Hi

40% --> 4/10, 30%-->3/10
3/10 of Box A = 4/10 of Box B + 60
12/40 of Box A = 12/30 of Box B + 60
Numerator --> 12 units

cheers.

[AJH]

:scratchhead: :scratchhead: Hi - have trouble with these problems:


Q1. If Darren gives 12 of his seashells to Kim, he will have 4 times as many seashells as Kim. If Darren gives another 4 more seashells to Kim, he will have thrice as many seashells as Kim. How many seashells does Kim have? Ans: 4

Q2. A flask is 1/3 filled with chocolate powder. A teapot, twice as large as the flask, is 1/4 filled with chocolate powder. Then the flask and the teapot are each filled with water completely and all the contents are mixed together into a chocolate drink. What fraction of the chocolate drink is the chocolate powder?

I've got 7/12 but the ans is 5/18 :scratchhead:

Q3. There are 65 lamp posts along St. Andrew's Street. The lamp posts are arranged such that the distance between two lamp posts on the same side of the street is 20m. One lamp post is on the opposite side of the street at an equal distance between the two lamp posts. How long is St Andrew's Street? Ans: 640m

Thank you.

[MathIzzzFun]

isetan:

http://i47.tinypic.com/vzzksz.jpg\">


The figure is made up of a circle, identical semicircles and a square of side 12cm. P is the centre of the circle. What is the area of the shaded figure? Leave your answer correct to two decimal places.


Hi, can somebody helps this question? Thank u.

Hi

http://i46.tinypic.com/sg75p3.png\">

cheers.

[isetan]

MathIzzzFun:

isetan:

http://i47.tinypic.com/vzzksz.jpg\">


The figure is made up of a circle, identical semicircles and a square of side 12cm. P is the centre of the circle. What is the area of the shaded figure? Leave your answer correct to two decimal places.


Hi, can somebody helps this question? Thank u.

Hi

http://i46.tinypic.com/sg75p3.png\">

cheers.

Thanks MathIzzzFun. This question is from Henry Park Prelim 2011 Paper. However, the answer is 43.73cm2. Can u assist again?

[small]

Hi Isetan,


My answer is same as MathIzzzFun.

[isetan]

small:

Hi Isetan,


My answer is same as MathIzzzFun.

Thanks small. Please note that there is one small portion shaded (in my original attached diagram), just wonder have u taken into account?

[MathIzzzFun]

isetan:

MathIzzzFun:

http://i47.tinypic.com/vzzksz.jpg\">


The figure is made up of a circle, identical semicircles and a square of side 12cm. P is the centre of the circle. What is the area of the shaded figure? Leave your answer correct to two decimal places.


Hi, can somebody helps this question? Thank u.

Hi

http://i46.tinypic.com/sg75p3.png\">

cheers.

Thanks MathIzzzFun. This question is from Henry Park Prelim 2011 Paper. However, the answer is 43.73cm2. Can u assist again?

Hi
I never trust the answer key that is provided cos I have found many incorrect answers.

The given answer of 43.73 cm2 = 1/2 area of square - 1/4 circle of radius 6cm, which is incorrect.

Based on what I have, the shaded area does not include the one that I have circled in dotted line below.

http://i45.tinypic.com/y0v9s.png\">

Just to add that, if the circled area is included, the total shaded area is more than 51.45cm2. By the way, calculation of the circled area is not covered in the syllabus as this would require knowledge of trigo functions/pythagoras theorem.

cheers.

[isetan]

MathIzzzFun:

isetan:

[quote=\"MathIzzzFun\"]http://i47.tinypic.com/vzzksz.jpg\">


The figure is made up of a circle, identical semicircles and a square of side 12cm. P is the centre of the circle. What is the area of the shaded figure? Leave your answer correct to two decimal places.


Hi, can somebody helps this question? Thank u.

Hi

http://i46.tinypic.com/sg75p3.png\">

cheers.

Thanks MathIzzzFun. This question is from Henry Park Prelim 2011 Paper. However, the answer is 43.73cm2. Can u assist again?

Hi
I never trust the answer key that is provided cos I have found many incorrect answers.

The given answer of 43.73 cm2 = 1/2 area of square - 1/4 circle of radius 6cm, which is incorrect.

Based on what I have, the shaded area does not include the one that I have circled in dotted line below.

http://i45.tinypic.com/y0v9s.png\">

Just to add that, if the circled area is included, the total shaded area is more than 51.45cm2. By the way, calculation of the circled area is not covered in the syllabus as this would require knowledge of trigo functions/pythagoras theorem.

cheers.[/quote]Appreciate and Thanks for your help.