Q&A - PSLE Math

[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 100% = 40%
There are 40% less pens in Box B than in Box A.

cheers.

[mumworks]

:thankyou: very much Tianzhu for answering all my questions.

[kiasuaunt]

tianzhu:

kiasuaunt:

Hi.

Q1.
Mr Lee sold 15% of his cupcakes on Monday.
He sold 90 fewer cupcakes on Tuesday than on Monday.
He then sold 70 fewer cupcakes on Wednesday than on Tuesday.
On Thursday,he sold 330 cupcakes and found that he had half of his original number of cupcakes left.
How many cupcakes did he sell altogether?

Hi

A neat way is to use MD.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7220/7353643500_a0f577ed8d_z.jpg\">

:thankyou:

[pixiedust]

Here’s my solution :


girls:boys -> 3:2 -> 6:4
women:boys -> 5:4
girls:men -> 2:5 -> 6:15

girls:boys:women:men -> 6:4:5:15

At first : women:men -> 5:15 -> 1 :3
end : women: men -> 1:2

women : men
1u : 3u
-6 : -27
---------
1p: 2p

hence, 2u-12=3u-27; u=15
so we know, women at first = 1u = 15; men at first = 3u = 3*15=45
therefore (a) 15/45=1/3

since girls:boys:women:men -> 6:4:5:15
and women=15,men=45, therefore, (b) children=(6+4)*3=30

[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.

[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.