Q&A - PSLE Math

[kklau]

Hi Tianzhu,


Many thanks for your reply and the mentioned P6 Maths question was taken from South View Pri. School revision paper, the diagram was re-drawn and the shaded areas could be differs. Perhaps your diagram could be the correct one!

Thank you again for pointing the error and looking forward for your good solution soon.

Best Regards.

[rose michelle]

The figure below shows 3 different rectangles, X, Y ad Z. 3/10 of X and 40% of Z is shaded. The shaded area of X is the same as the shaded area of Z. What fraction of the figure is unshaded if 60% of Y is shaded?

[small]

tianzhu:

kklau:

Hi,


Re-post and I would be very much appreciate that anyone could help to provide solution to this P6 maths question.

The diagram below 2 quadrants and a circle in a square of edge 10cm. Find the area of the shaded region (Take π = 3.14)

http://i47.tinypic.com/10fv18n.png\">

Thank you.

Best Regards.

Hi

Could you share where is your question from?

I've seen one similar question some years ago, but the shaded areas differs slightly.

Best wishes

http://farm8.staticflickr.com/7089/7152307519_7fa3e70673_z.jpg\">

Hi kklau,

I hope my working will not confuse you.

http://i47.tinypic.com/33x78nn.jpg\">

[speedmaths.012624com]

Winx5015:

Hi, need help for the following questions.


(1). The time taken for 10 workers to complete a construction job is 6 days more than the time taken for 12 workers to finish the same job. What is the number of workers required so that the time taken to finish the construction job is 21 days less than the time 10 workers took?

Hi,

Ratio of workers is 10:12.
Ratio of time taken will be 12:10, or 36:30.

10 workers will take 36 days; Job → 10 x 36 → 360 man-days.
12 workers will take 30 days; Job → 12 x 30 → 360 man-days.

10 workers will take 36 days.
Number of workers needed to complete job in (36 - 21 or) 15 days is:
360 man-days / 15 days → 24 workers.

Hope this helps.

Cheers


speedmaths.com


.

[MathIzzzFun]

Winx5015:

Hi, need help for the following questions.


(1). The time taken for 10 workers to complete a construction job is 6 days more than the time taken for 12 workers to finish the same job. What is the number of workers required so that the time taken to finish the construction job is 21 days less than the time 10 workers took?

(2). If Allan and Bob work together, they can complete a job in 12 days. If they work together for 3 days, followed by Bob who worked alone for the next 5 days, they can finish 5/12 of the job. How many days will each of them need to complete the job if they were to work alone?

(3). Pool A and Pool B were filled to the brim with water. The taps at Pool and Pool B were turned on at 1pm and 2.30pm respectively to empty the pools. At 5pm, the water level in both pools were the same. At 6.30pm, Pool B was completely empty while Pool A was still filled with water. At 7pm, Pool A was completely empty. It was given that Pool A was 0.8 higher than Pool B in depth. If the rate of flow of water from each tap was kept constant, what was the height of Pool A.

Thanks!

Hi

Q3.
Total time taken for Pool A to empty = 1900h - 1300h = 6h
Total time taken for Pool B to empty = 1830h - 1430h = 4h
At 5pm,
Pool A → 2/6 = 1/3 filled with water
Pool B → 1.5/4 = 3/8 filled with water
1/3 A = 3/8 B
3/9 A = 3/8 B
A--> 9 units, B --> 8 units
1 unit → 0.8m
Pool A → 9 x 0.8m = 7.2 m
Pool B → 8 x 0.8m = 6.4 m

cheers.

[MathIzzzFun]

Winx5015:

Hi, need help for the following questions.


(2). If Allan and Bob work together, they can complete a job in 12 days. If they work together for 3 days, followed by Bob who worked alone for the next 5 days, they can finish 5/12 of the job. How many days will each of them need to complete the job if they were to work alone?

Thanks!

Hi

Q2.
Allan & Bob --- 12 days --> 12 units of work
Allan & Bob -- 3 days --> 3 units of work

Bob -- 5 days --> 5-3 = 2 units of work
Bob -- 12 units of work --> 12/ 2 x 5 = 30 days

Allan & Bob --- 5 days --> 5 units of work
Allan -- 5 days --> 5 - 2 = 3 units of work
Allan -- 12 units of work --> 12 /3 x 5 = 20 days

cheers.

[tianzhu]

Hi kklau


Good Morning.

What I am sharing is one similar question which my kid had done years ago.

If the question is shaded as I’ve drawn, then you may follow the steps as shown in this slide.I've attempted to breakdown the composite figure into familiar shapes.Please get your child to work out the other details.

Please take note that this is a possible way, there are alternatives.

Usually, the calculations in questions on composite figures are quite neat, just applying the formulae and pressing the calculators. But, the difficulties many students faced are visualising and rearranging the shapes into familiar shapes. This is the part which tripped many students.

You may also refer to small’s solution.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7041/7154653294_de8b0cc591_z.jpg\">

[tianzhu]

Winx5015:

(2). If Allan and Bob work together, they can complete a job in 12 days. If they work together for 3 days, followed by Bob who worked alone for the next 5 days, they can finish 5/12 of the job. How many days will each of them need to complete the job if they were to work alone?

Hi

Good Morning.

A similar question has been discussed before.

Hope this helps.

Best wishes.

http://farm5.staticflickr.com/4053/4715375219_19cfa8eb65_z.jpg\">

[Winx5015]

Thanks speedmaths.com , MathIzzzFun and tianzhu for your solutions.


Really appreciate your help

[tianzhu]

superhappy:

Hi, need help on this questions
1. Varsha had some 20-cent and 50-cent coins.
7/8 of the coins were 20-cent coins and the rest were 50-cent coins.
After Varsha had spent $72.50 worth of 50-cent coins and 5/7 of the 20-cent coins, she had 2/7 of coins left. Find the total amount of money Varsha left.

Hi

This question has been discussed before.

Hope this helps.

Best wishes

http://farm8.staticflickr.com/7054/6835330158_899602206e_z.jpg\">