Q&A - PSLE Math

[N3SKiasu]

Hi all,

Need your help on this Rosyth Prelim 2008 Q48 (I have searched thru past pages and could not find any discussion on this question, hope my eyes are working fine by browsing thru the 50+ pages and it is not repeated):

Ning and Zongwei jogged to and fro repeatedly along a straight path in a park between 2 points A and B.
Ning jogged at a uniform speed of 4m/s.
Zongwei jogged at uniform speed of 6m/s.
They started jogging from opposite directions at the same time as shown below.
Ning ------> <----------Zongwei
A---------------------X---------------------Y-------------------B

They first met one another at point X. The second time they met was at point Y.
a) Given that the distance between X and Y is 160m. Find the distance between A and B. (Answer given : 400m)
b) If they started jogging at 8am, how long did they take to meet again for the third time? (Express your answer in minutes and seconds). (Answer given : 3m20s)

Do you consider this is as a challenging question?
A bit worried for DD now as she could not solve this sort of question at this point...and so do I, helpless mom...counting down...
TIA.

[N3SKiasu]

Would like to check on the answer for SCGS Prelim 2008 Q23:


A 200m long MRT train took 20 min to pass through a tunnel completely.
If the MRT train travelled at an average speed of 120 m/min, find the length of the tunnel.

Solution:
120m/min x 20 min = 2400 m
2400m - 200 m = 2200m

But the answer given is 2300 m. Just wondering if the answer given is correct?

[tianzhu]

N3SKiasu:

Hi all,

Need your help on this Rosyth Prelim 2008 Q48 (I have searched thru past pages and could not find any discussion on this question, hope my eyes are working fine by browsing thru the 50+ pages and it is not repeated):

Hi
Dharma had answered this Q.Please go to pg 54.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=795

[tianzhu]

N3SKiasu:

120m/min x 20 min = 2400 m
2400m - 200 m = 2200m
But the answer given is 2300 m. Just wondering if the answer given is correct?

Hi
You are right.
The answer is 2200m.

[N3SKiasu]

tianzhu:

N3SKiasu:

Hi all,

Need your help on this Rosyth Prelim 2008 Q48 (I have searched thru past pages and could not find any discussion on this question, hope my eyes are working fine by browsing thru the 50+ pages and it is not repeated):

Hi
Dharma had answered this Q.Please go to pg 54.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&postdays=0&postorder=asc&start=795

Thank you so much Tianzhu, oh it was just 3 pages before this, I must have browsed thru too quickly. Millions thanks!

[N3SKiasu]

tianzhu:

N3SKiasu:

120m/min x 20 min = 2400 m
2400m - 200 m = 2200m
But the answer given is 2300 m. Just wondering if the answer given is correct?

Hi
You are right.
The answer is 2200m.

Thanks again Tianzhu for the confirmation.

[k1ndan]

Four Friends, Alice, Billy, Carol and David shared a total of 81 chocolates. Alice received 4/5 of the total number of chocolates received by Billy. Carol and David. Billy received 2/3 of the total number of chocolates received by Carol and David. Carol received twice as many chocolates as David.


(a) What fraction of all the chocolates does Billy have?

(b) How many chocolates did Alice receive?

[Sahimi]

a) A : B+C+D

4 : 5

B : C+D
2 : 3


A : B : C : D
4 : 2 : 2 : 1

81 divide by 9 times 2 = 18
18/81 = 2/9

b) 1u = 81 divide by 9 = 9
9 times 4 = 36

[James Ang]

My students are practising these common question types for the PSLE paper in 1 week’s time.



1. John cycled at an average speed of 10km/h from his home to the park. On reaching the park, he cycled back home along the same route at an average speed of 8km/h. He took 1h 12 mins for the entire journey. How long did he take to cycle from the park back to his home?

2. Jack bought some pens and erasers for a total of $100.10. He spent $9.10 more on the pens than erasers. Each pen costs $3.70 more than each eraser. Jack bought 7 times as many erasers as pens. How much does a pen cost?

3. Andy sold thrice as many $5 T-shirts as $10 T-shirts. He also sold twice as many $10 T-shirts as $20 T-shirts. He collected $160 more from selling $5 T-shirts than from selling $20 T-shirts.

a)\tHow much money did he collect from selling $5 T-shirts?
b)\tHow many T-shirts did he sell altogether?

4. Tom and Jerry each has some money. If Tom spends $9 per day and Jerry spends $3 per day, Tom will have $100 left when Jerry has spent all his money. If Tom spends $3 per day and Jerry spends $9 per day, Tom will have $220 left when Jerry has spent all his money. How much did Jerry have?

5. A van travelled from Town A to Town B at an average speed of 55km/h. A car started its journey from town B to A at 90 km/h at the same time the van started. The two vehicles passed each other 70 km from the middle of the whole journey. Find the distance between the two towns.

6. 80% of marbles are red marbles and 20% of them are blue marbles. 63 red marbles and 46 blue marbles are added. The red marbles now makes up 75% of marbles and blue marbles 25% of marbles. How many red marbles are there at first?

7. Courier A takes 10 hours to deliver a parcel from Town X to Town Y. Courier B takes 12 hours to deliver the parcel along the same route. If the speed of Courier A is 9km/h faster than that of Courier B, find the speed of Courier A.

8. In a concert, 75% of the audience were female. 75 females and 5 males left the concert half way. The remaining audience were allocated seats in groups of 10. Each group has 3 males. How many people were in the audience at first?

9. On Linda’s birthday, she gave sweets to every pupil in her class. If she gave each pupil 7 sweets, she would have 4 sweets left. If she gave 2 sweets to each pupil, she would have 189 sweets left. How many pupils were there in Linda’s class?

10. The ratio of Ryan’s pocket money to John’s pocket money was 3 : 2. After Ryan saved $15 and John spent $8, the ratio of Ryan’s pocket money to John’s pocket money was 3 : 1. How much money did Ryan have at first?

11. A lorry left Town A for Town B. After travelling for 4 hours at its usual speed, the lorry stopped for 30 mins for a break. In order to reach Town B at the appointed time, the speed of the lorry was increased by 8 km/h. Given that the lorry took 3 hours to cover the remaining journey, find the distance between Town A and Town B.

12. Paul and Ray worked together to paint a house. During the job, Paul rested for 4 days and Ray took 2 days off. However, they were not absent on the same days. If they had done the same job alone, Paul would have taken 18 days and Ray 12 days. How long did the two painters take to complete painting the house?

[Muffins]

A : B+C+D

4u : 5u

4u + 5u = 9u which is 81
81/9 = 9
1 unit = 9

a) 2u= 2X9 = 18
9X9 = 81
18 : 81 = 2 : 9

b) 81 X 4/9 = 36

That's the method I got!