Q&A - PSLE Math

[tianzhu]

Hi noob


You’re welcome.

Best wishes

[trytry]

Mickey and Minnie worked together to paint a house.

During the process, Mickey took 9 days off and Minnie took 2 days off.
However, they were not absent on the same days.
If they had done the job alone, Mickey would have taken 15 days and
Minnie would have taken 18 days.
How long did Mickey and Minnie take to finish painting the house?
(Pei Hwa Pres SA1 Q18 2010)
TIA.

[atutor2001]

trytry:

Very bad on rate questions, pls help me


Mickey and Minnie worked together to paint a house.
During the process, Mickey took 9 days off and Minnie took 2 days off.
However, they were not absent on the same days.
If they had done the job alone, Mickey would have taken 15 days and
Minnie would have taken 18 days.
How long did Mickey and Minnie take to finish painting the house?
(Pei Hwa Pres SA2 Q18 2010)
TIA.

In 1 day Mickey can paint 1/15 of the house = 6/90 of the house
In 1 day Minnie can paint 1/18 of the house = 5/90 of the house
In 1 day Mickey + Minnie can paint 6/90 + 5/90 = 11/90 of the house

In the 9 days that Mickey was off, Minnie painted 5/90 x 9 = 45/90 of the house.
In the 2 days that Minnie was off, Mickey painted 6/90 x 2 = 12/90 of the house.

Total Amount painted in those 11 days = 45/90 + 12/90 = 57/90

Amount left to be painted = 90/90 - 57/90 = 33/90

When both of them paint together, they need another 33/11 days = 3 days

Total no. of days needed = 11 + 3 = 14 days (ANSWER)

[trytry]

Thanks atutor2001. I understand now.

[meimeitan]

Hi! All,


Can solve the following question?

June Jie bought some candies that came in square pyramid packages. Each pyramid had a square base area of 1 cm square and a vertical height of 1 cm. He then packed the candies in a box measuring 6 cm by 4 cm by 4 cm. What was the maximum number of such candies he could pack into the box?

thanks.

[atutor2001]

meimeitan:

Hi! All,


Can solve the following question?

June Jie bought some candies that came in square pyramid packages. Each pyramid had a square base area of 1 cm square and a vertical height of 1 cm. He then packed the candies in a box measuring 6 cm by 4 cm by 4 cm. What was the maximum number of such candies he could pack into the box?

thanks.

The first layer can have 6 x 4 = 24 pyramids.

Turn the pyramids upside down (invert) to sit in the first layer, we get 5 x 3 = 15 pyramids

That means for every 1 cm height of the box, we can pack 24 + 15 = 39 pyramids.

Total height of 4cm can pack 39 x 4 = 156 (is it correct?)

Below is my best attempt of presenting the picture for stacking of 5 pyramids (looking from the top) - 4 upright pyramids and 1 inverted in the centre. The pattern can be repeated for each layer for 6cm x 4cm.
_______
| .._|_....|
|_|_|_|_.|
| .|_|_|...|
|__.|__..|

[meimeitan]

Hi!


thanks for your prompt reply. The answer given is 176 and the word maximum is underlined and bloded to remind students that the answer should be miximum. Any idea?

thanks :lol:

[atutor2001]

meimeitan:

Hi!


thanks for your prompt reply. The answer given is 176 and the word maximum is underlined and bloded to remind students that the answer should be miximum. Any idea?

thanks :lol:

Sorry lah. I think high think low, think left, think right, still can't put in the extra 20 pyramids. Hopefully one of the experts here will post the correct method soon.

[Brenda10]

Hi all, need your help on the following question.



Rosyth 2010 CA1 P2 Q16 (given answer Fazillah:39, Linda: 35)

Fazillah, Linda and Winnie each owned a collection of comics. The total collection owned by Linda and Winnie was 3/2 as many comics as Fazillah owned. Linda owned 4/5 as many comics as the total collection owned by Fazillah and Winnie. If Winnie owned 169 fewer comis than Linda, how many comics must Fazillah and Linda each give to Winnie in order for the three girls to have the same number of comics ?

Thank you

[Vanilla Cake]

Brenda10:

Hi all, need your help on the following question.

Rosyth 2010 CA1 P2 Q16 (given answer Fazillah:39, Linda: 35)

Dear Brenda10,
Checked with my younger sister's papers for this school and the given answers are correct ie Fazillah: 39 and Linda: 65

Brenda10:

Fazillah, Linda and Winnie each owned a collection of comics. The total collection owned by Linda and Winnie was 3/2 as many comics as Fazillah owned. Linda owned 4/5 as many comics as the total collection owned by Fazillah and Winnie. If Winnie owned 169 fewer comis than Linda, how many comics must Fazillah and Linda each give to Winnie in order for the three girls to have the same number of comics ?

My younger sister's workings
L+W : F
3 : 2
27 : 18

L : F+W
4 : 5
20 : 25

F: 18u
L: 20u
W: 7u

13u=169

(18u+20u+7u)/3=15u
18u-15u=3u
3u=39 (F)
20u-15u=5u
5u=65 (L)

Fazillah and Linda must gave up 39 comics and 65 comics respectively to Winnie in order for the three girls to have the same number of comics.

Off topic, you had mentioned in another thread that you had bought some science assessment books for your DD to read and understand how these answers are worded. If you don't mind, pls share the title of these books.Also thks for your reply for the 2 questions on P6 English in another thread.