Q&A - PSLE Math

[smileplease]

tianzhu, thank you very much. Your workings are always easy to understand. You are better than the school teacher.


Most of the time, my daughter’s teacher use Model method which we cannot comprehend at all.

[tianzhu]

Hi


In doing this question, students need to watch out for the difference between number of dollar notes and value of dollar notes.

As usual, I’ve drawn more MD than necessary to show the flow of events.

To all PSLE kids, wishing you the very best for your Maths paper tomorrow.

Good luck and have a good rest tonight.

Best wishes.

http://farm7.static.flickr.com/6004/6194964658_431822003d_z.jpg\">

[Verysuperkiasu]

tianzhu:

This question from SCGS Prelim 2009 looks quite the same as the one shown in the figure.

Please see if it is useful to you.

Best wishes.

http://www.kiasuparents.com/kiasu/forum/viewtopic.php?f=69&t=280&start=1980

Thank you so much, tianzhu!

[Verysuperkiasu]

cchew:

Notice that when the big circle added to the 2 semi circle, the common area between the semicircle and circle is duplicate.

Thank you for your help!

[Verysuperkiasu]

Vanilla Cake:

Q11 and answer given : 54720 cm2

http://i51.tinypic.com/34s2yw4.png\">

posted by VC's mum

if it's not too much to ask, pls help to post the above solution. My son got a very different answer.

[tianzhu]

Verysuperkiasu:

if it's not too much to ask, pls help to post the above solution. My son got a very different answer.

Hi

Design A

Area of 1 square (10*10) ------100
Area of 4 squares -------400

Area of 1 circle (r5) ------ 78.5
Area of 8 circles -------628

Shaded area ------- 1028 (400+628)

Design B

Area of big square(40*40) -------- 1600
Area of shaded area ------1600 – 1028 -----572

Difference in shaded area ------1028 – 572 ------456

6m*3.2m ------ needs 15*8 pieces of 40cm*40cm squares

More area -------456*15*8 ------ 54720.

Best wishes

[P6ians]

Dear VC's mum,

Here's the solution:
For design A,
40/8=5(radius of one small semicircle in the design)
area of one \"flower\"--- 3.14x5x5x2=157
157+(10x10)
=257
Area of shaded parts:257x4=1028
The total area bob plans to cover:600x320=192000
sets of (40x40) in 192000=120 sets
Hence,
120x1028=123360(total area painted by Bob if he uses design A)
Now foR design B:
257x4=1028
(40x40)-1028=572
572x120=68640(total area painted by bob for design b)
123360-68640=54720(answer)
Hope this helps!

[Verysuperkiasu]

tianzhu:

Area of big square(40*40) -------- 1600
Area of shaded area ------1600 – 1028 -----572

Difference in shaded area ------1028 – 572 ------456

6m*3.2m ------ needs 15*8 pieces of 40cm*40cm squares

More area -------456*15*8 ------ 54720.

Best wishes

Thank you so very much!!!

[ck123]

Hi


How many digits are there from 1-99?

Thanks

[tianzhu]

ck123:

Hi


How many digits are there from 1-99?

Thanks

Hi

Page 1 to page 9 ------- 9 digits
Page 10 to page 99 ------- (99-10) + 1 -------90 pages ------- 90*2 ------- 180 digits

Number of digits -------189.

Best wishes