Q&A - PSLE Math

[smileplease]

Need help on this Q :


Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he made?

thank you.

[ck123]

Hi can confirm question 15 of nanyang prelim 2011 answer is 428 2/3 mins or 428 4/7 mins

Thanks

[smileplease]

It should be 428 2/3 mins. This part is tricky, this is the detailed solution my friend gave me.


Vol of tank = 3x3x15 = 13.5 m3 x1000 = 13,500 l
Vol of water = 1/3 x 13.5 =4.5 m3 x1000 = 4500l
13500 – 4500 = 9000 l
2min => water filled = 18x2 = 36l +6l = 42l
9000 / 42 = 214 12/42 = 214 2/7 of 2 min
214x2 =428min , water filled = 42 x 214 =8988 l
9000 – 8988 =12l
1min =18l
12l = 1/18 x12 = 2/3 min
Total time taken = 428 + 2/3 = 428 2/3 min

[ck123]

:thankyou: smileplease got it

[tianzhu]

smileplease:

Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he made?

Hi

Mon ------- 2 units
The remaining 8 units is subdivided into 27 (Tues) + 1 part (Wed) + 9 parts left.

8 units – 27 ------ 10 parts -------E1
5 units + 1 ------ 9 parts ------- E2

Multiply E1 by 9 and E2 by 10

72 units – 243 ------ 90 parts
50 units + 10 ------- 90 parts

22 units --------253
1 unit ------- 11.5

10 units ------ 115.

Best wishes

PS ------ The total number of 115 is a whole number which looks logical. However base on this figure, the number of toys sold on Wed is 6.5, which doesn’t seem right. Please check with the source of your question.

[Verysuperkiasu]

kavisuresh:

Pls help to solve:

The fig below is made up of a circle, a triangle and two identical semicircles. The diametre of the circle is 8cm and the diametre of the semicircle is 4cm. Find the area of the shaded regions.

http://i54.tinypic.com/11vnyv8.jpg\">
thanks.

may i know anyone has the answer/sol to this?

[tianzhu]

Verysuperkiasu:

kavisuresh:

Pls help to solve:

The fig below is made up of a circle, a triangle and two identical semicircles. The diametre of the circle is 8cm and the diametre of the semicircle is 4cm. Find the area of the shaded regions.

http://i54.tinypic.com/11vnyv8.jpg\">
thanks.

may i know anyone has the answer/sol to this?

Hi

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

[cchew]

Verysuperkiasu:

kavisuresh:

Pls help to solve:

The fig below is made up of a circle, a triangle and two identical semicircles. The diametre of the circle is 8cm and the diametre of the semicircle is 4cm. Find the area of the shaded regions.

http://i54.tinypic.com/11vnyv8.jpg\">
thanks.

may i know anyone has the answer/sol to this?

The big circle + 2 semi circle - the triangle = answer

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

[smileplease]

tianzhu:

smileplease:

Mr Samad made some toys to sell. He sold 20% of the toys on Monday. He sold 27 toys on Tuesday. On Wednesday he sold 10% of the remaining toys. After that he found that the toys he had left was 1 more than 1/2 the number of toys he had made. How many toys did he made?

Hi

Mon ------- 2 units
The remaining 8 units is subdivided into 27 (Tues) + 1 part (Wed) + 9 parts left.

8 units – 27 ------ 10 parts -------E1
5 units + 1 ------ 9 parts ------- E2

Multiply E1 by 9 and E2 by 10

72 units – 243 ------ 90 parts
50 units + 10 ------- 90 parts

22 units --------253
1 unit ------- 11.5

10 units ------ 115.

Best wishes

PS ------ The total number of 115 is a whole number which looks logical. However base on this figure, the number of toys sold on Wed is 6.5, which doesn’t seem right. Please check with the source of your question.

You are correct. BUt this is from 2010 River Valley Math prelim Paper 2 Q10.

[smileplease]

Another one Q :


Mrs Lim had twice as many ten-dollar notes as two-dollars at first. She bought a digital camera for $288 and paid for it with thrice as many two-dollar notes as ten-dollar notes. Then she realised that she had 4 times as many ten-dollar as two dollar notes left.
a) how many pieces of two-dollar notes did Mrs Lim have at first?
b) how much money had Mrs Lim left after buying the digital camera?

thank you.