Q&A - PSLE Math

[BryBenMum]

Hi,

Please help with this question,
Ailing, Bala, Chris and Dawn shared the cost of a gift for their friend. Ailing paid 1/5 of the amt paid by Bala, Chris and Dawn. Chris paid 40% of the amt paid by Ailing and Bala. The total amt paid by Ailing and Bala is equal to that paid by Chris and Dawn. Given that Dawn paid $32 more than Ailing for the gift, what was the cost of the gift?
Thank you![/list]

[BryBenMum]

Hi,

Please help with this question,
Ailing, Bala, Chris and Dawn shared the cost of a gift for their friend. Ailing paid 1/5 of the amt paid by Bala, Chris and Dawn. Chris paid 40% of the amt paid by Ailing and Bala. The total amt paid by Ailing and Bala is equal to that paid by Chris and Dawn. Given that Dawn paid $32 more than Ailing for the gift, what was the cost of the gift?
Thank you![/list]

[abc_parent]

Hi gurus,

I have some questions from various papers 1.

NanHua SA1 2009

Q14) Adrian and Bob started driving at the same time. Bob took 6 hours to complete his journey while Adrian took 9 hours to complete his. After 3 hours ,the two men were left with the same distance to complete. What is the ratio of the distance of Bob's journey to the distance of Adrian's journey?

Ans: 4:3


Nan Hua Prelims 2009

Q14) Which one of the following shapes does not tessellate? -> I don't have picture so please help if you can.

Ans: (4) is the given answer correct?

Catholic High Prelims 2009

Q30) A man travels from Town X to Town Y at 4km/h and from Town Y to Town X at 6 km/h via the same route. The whole journey takes 45 minutes. Find the distance from Town X to Town Y.

Ans: 1.8km (how? I got 3.8km)

SCGS Prelims 2009

Q15) Alan completed a race in 1h 40 min. In the race, the ran at an average spped of 30m/min from Point A to Point B and then ran back from Point B to Point A at an average speed of 20m/min. How long did he take to run back to Point A from Point B?

Ans: I don't have it. Choices of 40 min, 50 min, 60 min, 100 min.

Nanyang Prelims 2009

Q15)This question has a diagram. Please help if you have the exam paper.
The 4 containers below each contains the same amount of water with different number of objects. What is the volume of object Y?

Ans: Given answer is 80 cubic cm.

[Dharma]

Vanilla Cake:

tianzhu:

Maha Bodhi P6 Prelim 2010: Paper 2: Q16. Tom and Jerry shared a box of marbles. If Tom was given 10 fewer marbles, Jerry would have five times as many marbles as Tom. If Tom was given 10 more marbles, he would have ½ as many marbles as Jerry. What percentage of the marbles did Tom receive? [5 marks][Answer given: 25%]


Hi VC

Have you tried this question?
Could you get the same answer as given in the WS?

You may use MD.

Before
Tom -------1u+10
Jerry -------5 units

After
Tom ------- 1u+10+10
Jerry ------- 2units+40

3 units ------40
1unit ------40/3

Tom ------- 40/3+10 ----- 70/3
Jerry -------200/3

Total number of marbles ------- 200/3+70/3 --------90

Tom/Total ---------70/3/90*100 ------- 25 25/27% (25 and 25/27%)

Best wishes

Dear Uncle Tianzhu,

Sorry for the late reply as I had accompanied my mum to the wet market, this morning.Thanks for highlighting and after reading your post, I went to look at my calculations again and also went to http://psle2010a.blogspot.com/2010/09/maha-bodhi-p6-prelim-2010-paper-2-q16.html.
Both of you got 25 and 25/27%. It's the way of interpretation of the question that matters. My one is different from both of you and pls don't laugh at me (just joking) if I am wrong. Using unit and part method that Uncle Dharma usually uses, pls correct me along the way:

Case 1
T = u+10
J = 5u-10

Case 2
T = p-10
J = 2p+10

2p+10=5u-10
2p =5u-20
p = 2.5u-10

u+10=p-10
u+10=2.5u-20
30=1.5u
u=20
p=40

T = u+10 = 20+10 = 30 or p-10 = 40-10=30
J = 5u-10 = 5(20)-10 =90 or 2p+10 = 2(40)+10 = 90
Total of T + J = 30+90=120

Percentage of the marbles received by Tom =30/120x100% = 25%

Hi Vanilla Cake,

I agree with Tianzhú on this qns.

Jerry : 10u - 50
Tom : 2u – 10

Jerry : 4u + 20
Tom : 2u + 10

10u – 50 = 4u + 20
6u = 70
2u = 70/3

Percentage of marbles Tom received
= 2u/(2u + 4u + 20) x 100%
= 70/3/[70 + 20] x 100%
= 70/270 x 100%
= 25 25/27%

[tianzhu]

Dharma:

Hi Vanilla Cake,

I agree with Tianzhú on this qns.

Jerry : 10u - 50
Tom : 2u – 10

Jerry : 4u + 20
Tom : 2u + 10

10u – 50 = 4u + 20
6u = 70
2u = 70/3

Percentage of marbles Tom received
= 2u/(2u + 4u + 20) x 100%
= 70/3/[70 + 20] x 100%
= 70/270 x 100%
= 25 25/27%

Hi Dharma

VC's answer is correct.

The key word here is shared.
If Tom receives 10 fewer marbles, it also means Jerry receives 10 more.

I wongly interpreted the question in my earlier post.

This question touches on internal transfer.

You may use MD.

Before
Tom -------1u+10
Jerry -------5u -10

After
Tom ------- 1u +10+10
Jerry ------- 2u + 40

Compare the MD between scenarios 1 and 2.
5u – 10 -10 ----- 2u + 40
1u ------ 20

Tom -------30
Jerry ------90

30/120*100 % ------- 25%

Best wishes

[Vanilla Cake]

BryBenMum:

Ailing, Bala, Chris and Dawn shared the cost of a gift for their friend. Ailing paid 1/5 of the amt paid by Bala, Chris and Dawn. Chris paid 40% of the amt paid by Ailing and Bala. The total amt paid by Ailing and Bala is equal to that paid by Chris and Dawn. Given that Dawn paid $32 more than Ailing for the gift, what was the cost of the gift?

A : B+C+D
1 : 5
5 : 25

A+B : C+D
1 : 1
15 : 15

A: 5u
B: 15u-5u = 10u
C+D: 25u-10u=15u

C paid 40% of A+B -> 40/100x15u=6u
15u-6u=9u

D-A = 9u-5u = 4u

4u-> $32
u -> $8

Cost of gift = 30u = 30x$8 = $240

OR

http://4.bp.blogspot.com/_NGNaLTzN5_U/SrG7uyyhrSI/AAAAAAAADok/8K8CRswYDRs/s1600-h/Maths0609SA2P2CHFractionQ16A.JPG.

[Vanilla Cake]

abc_parent:

NanHua P6 SA1 2009 paper 1

Q14) Adrian and Bob started driving at the same time. Bob took 6 hours to complete his journey while Adrian took 9 hours to complete his. After 3 hours ,the two men were left with the same distance to complete. What is the ratio of the distance of Bob's journey to the distance of Adrian's journey?

After 3 hours, distance to be completed was the same for Adrian and Bob.
Constant distance - to complete journey after 3 hours
Ratio of time
Bob : Adrian
6-3 : 9-3
3 : 6
1 : 2

Ratio of speed
Bob : Adrian
2u : 1u

Total distance travelled by:
Bob -> 2u (speed)x6 (time) = 12u
Adrian-> 1u(speed0x9 (time) = 9u

Ratio of the distance of Bob's journey to the distance of Adrian's journey = 12u : 9u = 4 : 3

abc_parent:

Nan Hua P6 Prelim 2009 Paper 1
Q14) Which one of the following shapes does not tessellate? -> I don't have picture so please help if you can.
Ans: (4) is the given answer correct?

http://i994.photobucket.com/albums/af63/Perseverance20/NanHuaP6Prelim2009Paper1Q14.jpg\">
Sorry, I don't know how to resize the image in order to make it smaller.
Pls tell us why you think option (4) is not correct.

abc_parent:

Catholic High P6 Prelim 2009 paper 1
Q30) A man travels from Town X to Town Y at 4km/h and from Town Y to Town X at 6 km/h via the same route. The whole journey takes 45 minutes. Find the distance from Town X to Town Y.

Constant distance
Ratio of speed
4 : 6
2 : 3

Ratio of time
3 : 2

Total time taken = 45 minutes = 3u+2u = 5u
5u -> 45 min
u -> 9 min

If the man travels at 4 km/h then time taken = 3u = 3x9min = 27 min = 27/60 h
Distance between Town X and Town Y = 27/60x4 = 1.8 km

abc_parent:

SCGS P6 Prelim 2009 paper 1
Q15) Alan completed a race in 1h 40 min. In the race, the ran at an average spped of 30m/min from Point A to Point B and then ran back from Point B to Point A at an average speed of 20m/min. How long did he take to run back to Point A from Point B?

Constant distance
Ratio of speed
A to B : B to A
30 : 20
3 : 2

Ratio of time
A to B : B to A
2 : 3

Total time taken = 1 h 40 min = 100 min
2u+3u = 5u
5u -> 100 min
Time taken for running from B to A = 3u = 100/5x3= 60 min

abc_parent:

Nanyang P6 Prelim 2009
Q15)This question has a diagram. Please help if you have the exam paper.The 4 containers below each contains the same amount of water with different number of objects. What is the volume of object Y?
Ans: Given answer is 80 cubic cm.

Refer to http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-Nanyang.pdf.
Assume the amount of water be u.

x+u=100 cm³
2y+u=200 cm³ - (1)
2y+3x+u=380 cm³ -(2)
y+2x+u = 240 cm³

(2)-(1)
3x=180 cm³
x=60 cm³
u=(100-60) cm³ = 40 cm³
y = 240 cm³-2x-u = (240-120-40)cm³ = 80 cm³
Volume of object Y = 80 cm³

Mods: Pls merge this post in this http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&start=1750.

[James Ang]

The solution supplied with the set of prelims paper is wrong for question 18 and it is solved using algebra, and in one of the step the solution showed 7 instead of 9. The correct answer is Vanilla = 72 and Chocolate = 138 after correcting for that wrong step. question 17 on the two candles is interesting, it is exactly the same as what

I mentioned weeks ago, source is a sec 1 textbook, but can be easily solved by drawing a model. Again the supplied solution uses algebra which p6 students may not be taught to solve using algebra.

Vanilla Cake:

Susan has some vanilla and chocolate sweets in her bag. If she adds 20 vanilla sweets into the bag, the percentage of vanilla sweets in the bag becomes 40%. If she adds 30 chocolate sweets, there will be 70% of chocolate sweets in the bag. How many vanilla and chocolate sweets does she have? [5 marks][Answer given: 64 vanilla sweets and 126 chocolate sweets]

Thank you for your time and effort. I appreciate your help as I think that the answer given is incorrect.

My answers are : Vanilla sweets: 72 and Chocolate sweets: 138
Took me about 10 min plus using 2 different methods to crack this problem sum.Pls help to clarify if I am correct or the given answer is correct.

[pslemum]

Anybody can help with this question:


Container x had thrice as many jelly beans as Container Y. After 15% of the jelly beans in container X and 20% of the jelly beans in container Y were transferred to container W, the number of jelly beans in container W increased by 39%. COntainer W had 834 jelly beans in the end. How many jelly beans were there in container X in the end?

[Suz855]

Hi,


Need help on the solution for the following question, thanks

A,B, C and D shared a box of pens. A received 20% of the total number of pens which B, C and D received altogether. B received 50% of the total number of pens which A, C and D received altogether. C received 80% of the total number of pens which A, B and D received altogether. D received 6 pens. How many pens were in the box at first?

Ans : 108
:oops: [/img]