Q&A - PSLE Math

[tianzhu]

Hi ABCDE


Good Morning

Your mum must be very happy. You are an independent learner.

Wishing you the very best for PSLE 2010.

Best wishes

[Dharma]

Hi ABCDE,


It is surely nice hear that our contributions here had inspired you. Keep up the good work and my best wishes to you for PSLE.

[Dharma]

kancheongmum:

Hi all just got ACS prelim 2010 from a friend. Suprisingly in my opinion is not as challenging as the others. Came across 2 questions from the paper and like you all to try.


1)Mdm Zhang packed some beads into 14 small boxes and 15 big boxes. There were equal number of beads in each small box and equal number of beads in each big box. Each big box contained 5 more beads than each small box. 3/8 of the beads were packed in small boxes. How many beads were there in each small box? (ans 9)

2) A tank measuring 80 cm by 60 cm by 55 cm was 1/5 filled with water. A tap was turned on to fill it up with water at a rate of 9L per min. Every 30 seconds after the tap was turned on, an iron ball with a volume 500 cm3 was dropped into the tank. How many iron balls would there be in the tank when the water level reached the brim? (ans 42 iron balls)

Q1)

1p = 1u + 5
14(1u)/15(1p) = 3/5
70u = 45p
70u = 45(1u + 5)
25u = 225
1u = 9 (No. of beads in each small box)

Q2)

Amt of volume required for water level to reach the brim
= 4/5 x 80cm x 60cm x 55cm
= 211200cm2

Every 30 secs (1/2 min)
Additional volume = (9000cm3 x ½ min) + 500cm3 = 5000cm3

211200cm3 divide by 5000cm3 = 42.24

When water level reaches the brim; there would be 42 iron balls in the tank already.

[Vanilla Cake]

Dharma:

kancheongmum:

Hi all just got ACS prelim 2010 from a friend. Suprisingly in my opinion is not as challenging as the others. Came across 2 questions from the paper and like you all to try.


1)Mdm Zhang packed some beads into 14 small boxes and 15 big boxes. There were equal number of beads in each small box and equal number of beads in each big box. Each big box contained 5 more beads than each small box. 3/8 of the beads were packed in small boxes. How many beads were there in each small box? (ans 9)

2) A tank measuring 80 cm by 60 cm by 55 cm was 1/5 filled with water. A tap was turned on to fill it up with water at a rate of 9L per min. Every 30 seconds after the tap was turned on, an iron ball with a volume 500 cm3 was dropped into the tank. How many iron balls would there be in the tank when the water level reached the brim? (ans 42 iron balls)

Q1)

1p = 1u + 5
14(1u)/15(1p) = 3/5
70u = 45p
70u = 45(1u + 5)
25u = 225
1u = 9 (No. of beads in each small box)

Q2)

Amt of volume required for water level to reach the brim
= 4/5 x 80cm x 60cm x 55cm
= 211200cm2

Every 30 secs (1/2 min)
Additional volume = (9000cm3 x ½ min) + 500cm3 = 5000cm3

211200cm3 divide by 5000cm3 = 42.24

When water level reaches the brim; there would be 42 iron balls in the tank already.

http://www.onsponge.com/forum/35-thinkingmathonsponge/5169-acs-2010-p6-prelim-maths-paper-2.html for the above 2 questions from ACS (P) 2010 P6 Prelim Maths Paper 2.

VC's mum

[pecalis]

tianzhu:

Hi


You may wish to try this interesting speed question.

At 0954 Mary left Everton Park and cycled towards Serene Park while Joy left Serene Park and cycled towards Everton Park. At 1004, the two cyclists passed each other. 5 minutes later, Mary reached Serene Park but Joy was 780 m from Everton Park.

(a) At what speed were the two cyclists approaching each other?
(b) Find the distance (in km) between Everton Park and Serene Park.

Best wishes

Mary took 10 mins to meet Joy and another 5 mins to complete the journey.
That is, she took 15 mins to complete the journey and at meeting point, she would have travelled 2/3 of the distance.
Joy took 10 mins to complete 1/3 of the distance.
Ratio of distance of Mary : Joy = 2 : 1 = 6 : 3
Mary completed 6 units in 15 mins but Joy has another 3 units to go.
3u = 780m
1u = 260m
(b) Total distance between the 2 parks = 6u = 6x260 = 1560m = 1.56km

(a) Mary's speed = 1560/15 = 104m/min
Joy's speed is half of Mary's, = 52m/min

[tianzhu]

Hi


You may wish to work on this question.

James had some money in his wallet with values between $60 to $150. If he buys the maximum number of water bottles he can afford at $7 each, he will have $1 left. If he buys the maximum number of towels at $9 each, he would have $3 left. What is the actual amount James had?

Best wishes

[ABCDE]

Dharma:

Hi ABCDE,


It is surely nice hear that our contributions here had inspired you. Keep up the good work and my best wishes to you for PSLE.

Thank u very much Uncle Dharma n Tianzhu 4 your wishes

[cycjca]

Hi all

I’m new here, dd1 taking her PSLE in less than 2 weeks time and too bad only found this place very recently.

In anycase, hope someone can show this hopeless mama how to solve some of these questions:

1) Mrs Chua has just enough money to buy 4 kg of crabs & 3 kg of prawns. However she bought 2 kg of crabs & 4 kg of prawns & had $4.50 left. If she exchanged the 3 kg of crabs with 3 kg of prawns, how much money would she have left?

2)Mr Tan had 200 apples and oranges.
1/3 of the apples and 1/4 of the oranges were rotten. He threw away 60 rotten fruits altogether. How many rotten oranges were there?

Have been waitg for her teacher to go thru the questions with them…but nothing as yet! so panicking. Thanks in advance!

[octopusmum]

Hi all

need to ask for solutions for these 2 questions from Rosyth Prelim 2010 paper:

1) A tour bus which left Kuala Lumpur at 10.30am was scheduled to reach Singapore by 5pm. After travelling for 2 hours at its usual speed, the bus stopped for 30 minutes due to some problems. In order to reach Singapore punctually, the bus increased its speed by 8.5km/h. Given that the bus took 4 hours to complete the rest of the journey, find the distance between Kuala Lumpur and Singapore.

2) Xiaver, Yati and Zul each had a certain number of stamps. At first, Yati had 200 stamps more than Xiaver and Zul had 3/4 the number of stamps Yati had. After Yati gave away 1/8 of her stamps to Xiaver, she had 60 fewer stamps than Xiaver. What was the ratio of the number of stamps Xiaver had to the number of stamps Yati had to the number of stamps Zul had at first? Give your answer to the simplest form

thks v much

[Vanilla Cake]

octopusmum:

Hi all

need to ask for solutions for these 2 questions from Rosyth Prelim 2010 paper:

Hi octopusmum,
Due to time constraint (as I need to go to sleep), pls refer to the solutions done by Uncle Tianzhu and Uncle Observer.

octopusmum:

1) A tour bus which left Kuala Lumpur at 10.30am was scheduled to reach Singapore by 5pm. After travelling for 2 hours at its usual speed, the bus stopped for 30 minutes due to some problems. In order to reach Singapore punctually, the bus increased its speed by 8.5km/h. Given that the bus took 4 hours to complete the rest of the journey, find the distance between Kuala Lumpur and Singapore.

Solution by Uncle Tianzhu
Original time from KL to Singapore ----- 6.5h\t\t\t\t\t\t
\t\t\t\t\t\t
Consider the second half of journey\t\t\t\t\t\t
\t\t\t\t\t\t
Time ------- 4: 4.5 ------- 8:9\t\t\t\t\t\t
Speed -------9:8\t\t\t\t\t\t
\t\t\t\t\t\t
1 unit -----8.5km/h\t\t\t\t\t\t
8 units ------ 68 km/h\t\t\t\t\t\t
\t\t\t\t\t\t
Distance between Kuala Lumpur and Singapore ------68*6.5 ----- 442km\t

OR

http://psle2010a.blogspot.com/2010/09/speed-p6-2010-rosyth-p2-q17.html

octopusmum:

2) Xiaver, Yati and Zul each had a certain number of stamps. At first, Yati had 200 stamps more than Xiaver and Zul had 3/4 the number of stamps Yati had. After Yati gave away 1/8 of her stamps to Xiaver, she had 60 fewer stamps than Xiaver. What was the ratio of the number of stamps Xiaver had to the number of stamps Yati had to the number of stamps Zul had at first? Give your answer to the simplest form

Solution by Uncle Tianzhu
At First\t\t
X ------8units\t\t
Y ------- 8 units+200\t\t
Z -------3/4 of Y\t\t
\t\t
In the End\t\t
X -------9 units + 25\t\t
Y ------7 units + 175\t\t
Z remains the same\t\t
\t\t
7units+175+60 ----- 9 units +25\t\t
1 unit ------105\t\t
\t\t
X ------- 105*8 ------ 840\t\t
Y -------1040\t\t
Z -------780 (3/4 of Y)\t\t
\t\t
Therefore X:Y:Z ---------- 42:52:39

OR

http://psle2010a.blogspot.com/2010/09/fraction-p6-2010-sa2-rosyth-p2-q18.html

OR

http://www.onsponge.com/forum/35-thinkingmathonsponge/4868-prelim-2010-rosyth-working-backwards.html.