Q&A - PSLE Math

[kavisuresh]

Pls explain the basis for selecting numbers for the following qn.


qn: The diagram below shows 2 different views of the same cube. The numbers on the faces of the cube are 1,2,3,4,5 aned 6. Fill in the missing numbers in the net below.
http://i56.tinypic.com/104hxrp.jpg\">

thanks.

[kavisuresh]

Please explain the solution:

1. Study the five layer block as shown below. It is built from 55 similar 1cm cubes and is painted green. Find the total surface area that is painted green.
http://i54.tinypic.com/s6nhtt.jpg\">


2.James had a box of Australia and Japan stamps. After losing 4 Australian stamps, 20% of remaining stamps were Australian stamps. When he lost another 6 Australian stamps and gave away 78 Japan stamps, 1/3 of what he had left were Australia stamps. How many stamps had he at first ?
(pls expl model and ratio method)

Thank you.

[kavisuresh]

Pls help to solve.

1. There are ___ hundredths in 186.42
(42 / 18642 / 2)

2.Mrs. Tan baked 60 more chocolate pies than banana pies. After she gave away 2/5 of the chocolate pies and 3/4 of the banana pies, she was left with 64 more chocolate pies than banana pies. How many chocolate pies did she bake at first ?

3. Gerald had $20 more than Tommy at first. After Gerald gave Tommy $60, Gerald had 1/3 as much money as Tommy. Find amt of money Gerald had at first ?

4. Krishnan spent $84 on some plates and 1/3 of remaining money on some cups. If he had 1/5 of original sum of money left, how much did she have at first ?
Thanks a lot.

[htn]

tianzhu:

htn:

Hi, please help.

Amanda has $280 more than John. After Amanda spent 20% of her money and John spent 50% of his money, Amanda has $260 more than John in the end. How much does John have at first?

Hi

You may use MD or UM.

At first
Amanda ------ 10 units + 280
John ------ 10 units

Spent
Amanda ------ 2 units + 56
John ------ 5 units

In the end ---- Left
Amanda ------ 8 units + 224
John ------ 5 units

Amanda has $260 more than John in the end.

8 units + 224 ----- 5 units +260

3 units ------36
1 unit -----12

John ------10 units ------10*12 ------120

Best wishes

tianzhu

Thank you for your help.

[tianzhu]

kavisuresh:

1. Study the five layer block as shown below. It is built from 55 similar 1cm cubes and is painted green. Find the total surface area that is painted green.
http://i54.tinypic.com/s6nhtt.jpg\">

Hi

Where is this question from?

We cannot read the question in full.

Assuming to be a portable toy structure not a fixed structure.This means the bottom of the structure is also painted.

When viewed from the front or the back, the left or the right, we can see (1+2+3+4+5) or 15 square faces.

When viewed from the top or bottom, we can see 25 square faces.

Number of square faces ------- 4*15 + 2*25 ------ 110

Surface area to be painted ------110*1*1 ------ 110 sq cm

Best wishes

[tianzhu]

htn:

tianzhu
Thank you for your help.

Hi

You’re welcome.

Best wishes

[Angel25]

Pls HELP!!



Roy jogged from his house to the playground and back at 10km/h. He reached home at 12.18pm. If he jogged at 3km/h slower, he would reach home at 1.30pm. If he wanted to reach home at 12.45pm to have his lunch, at what speed did he have to jog?

Thanks!!

[Daddy]

Thanks MathIsssFun,


For Q2 i did not understand. Please explain. Thanks
http://i53.tinypic.com/10hlv08.jpg\">

How did you come out the model for Sam?
Why $40 = to 10u?
Why 7u = 2u + 10 +80?

Thank.

[maths6a]

Hi need help with this qn.

Has anyone posted it yet? pl direct me to the page. Thanks.

A, B and C were standing in a straight line waiting for a race to start.
C was 300 m ahead of B and B was 100 m ahead of A. At 9 am, they started the race. A overtook B in 5 min. In another 5 min, A overtook C. If B's speed is 150 m/min, at what time did B overtake C?

Thanks in advance.

[MathIzzzFun]

Daddy:

Thanks MathIsssFun,


For Q2 i did not understand. Please explain. Thanks
http://i53.tinypic.com/10hlv08.jpg\">

How did you come out the model for Sam?
Why $40 = to 10u?
Why 7u = 2u + 10 +80?

Thank.

Hi

hope this explains..

http://i52.tinypic.com/4qfu2p.jpg\">

cheers.