Q&A - PSLE Math

[tianzhu]

Winx5015:

Wendy has 80 more stamps than Mary but 50 more stamps than Jean. Wendy gives 1/2 of her stamps to Mary. Then Mary gives 1/5 of her stamps to Jean. If Jean has 62 more stamps than Wendy, how may stamps does Mary have in the end?


(Can tell me how to solve this question? Thanks)

Hi

You may use MD or units.

At first

Mary ------ 10 units

Wendy ------ 10 units + 80

Jean ------ 10 units + 30

Wendy gives 1/2 of her stamps to Mary.

Wendy

Left ------ 5 units + 40

Gave ------ 5 units + 40

Mary ------- 15 units + 40

Then Mary gives 1/5 of her stamps to Jean.

Mary

Left ------ 12 units + 32

Gave ------ 3 units + 8

Jean ------ 13 units + 38

If Jean has 62 more stamps than Wendy, how may stamps does Mary have in the end?

13 units + 38 ------ 5 units + 40 + 62

8 units ------- 64

1 unit ------ 8

Mary ------ 12 units + 32 ------- 128

Best wishes

[Recia Lim]

Please help to solve this question and it will be best if you can provide explanation. Thanks!


Q18. Abdul, Bernard and Chi Hao were all standing in a straight line waiting for the race to start. Chi Hao was 300m ahead of Bernard and Bernard was 100m ahead of abdul. At 9am, they started the race. Abdul overtook Bernard in 5 mins. In another 5 mins, Abdul overtook Chi Hao. If Bernard’s speed is 150m/min, at what time did Bernard overtake Chi Hao.

[Winx5015]

Thanks tianzhu. Have a nice weekends

[Zhu99]

Recia Lim:

Please help to solve this question and it will be best if you can provide explanation. Thanks!


Q18. Abdul, Bernard and Chi Hao were all standing in a straight line waiting for the race to start. Chi Hao was 300m ahead of Bernard and Bernard was 100m ahead of abdul. At 9am, they started the race. Abdul overtook Bernard in 5 mins. In another 5 mins, Abdul overtook Chi Hao. If Bernard's speed is 150m/min, at what time did Bernard overtake Chi Hao.

150 x 5 = 750 m --- distance covered by B in 5 mins

100 + 750 = 850 m --- distance covered by A in (first) 5 mins

850 x 2 = 1700 m --- distance covered by A in 10 mins (overtook C)

1700 - 100 - 300 = 1300 m --- distance covered by C in 10 mins

1300/10 = 130 m/min --- speed of C

150 - 130 = 20 m/min --- difference in speed between B and C

20 m ---> 1 min

300 m ---> 300/20 x 1 = 15 min --- 9.15 a.m.

Bernard overtook Chi Hao at 9.15 a.m.

[nounou]

http://i48.tinypic.com/2zexfzn.jpg\"> Please help to answer this Q. From Nanyang Prelim 2012 Q14. :imdrowning:

:thankyou: :thankyou: :thankyou:

[Michaelia0816]

Thx you for the Ali and Ahmad question, Tianzhu!

[peggy]

Please assist with this.


Ken and Peter went shopping with a total of $90. Ken spent twice as much as Peter. Ken had spent $5 more than the amount that he had left. In the end, Peter had thrice as much money left as Ken.

A) how much money did Peter spend?
B) how much money did Ken have at first ?

Thanks!

[MathIzzzFun]

Treelodge:

http://i48.tinypic.com/2zexfzn.jpg\"> Please help to answer this Q. From Nanyang Prelim 2012 Q14. :imdrowning:

:thankyou: :thankyou: :thankyou:

The attached drawing will be helpful to see the \"transfers\" of areas to make the shaded areas more recognisable ..


http://i48.tinypic.com/2chq8zm.png\">

Shaded area in Figure A --> 6 x orange area = area of 2 circles.
Shaded area in Figure B --> area of 1 circle (centre) + 6 x blue area = area of 1 circle + 6 x 1/6 of area of 1 circle = area of 2 circles.

cheers.

[kuts]

tianzhu:

kuts:

Help please.... from Tao Nan Prelims 2012

Thanks Tianzhu for the simplified explanation



1. There was some water in a container. Felicia first poured out 1/2 of the water. The she poured out 1/3 of the remaining water. In the third pouring, she poured ouot 1/4 of the remaining water and so on. How many times pouring will there be for the remaining water to be exactly, 1/10 of the original amount of water in the container?


Thanks in advance!

Hi

Try to see the pattern of 1/(n+1) for the remaining amount of water, where n refers to the number of pourings

In this case, it’s the 9th pouring.

Best wishes

[kuts]

ksme:

kuts:

Can anyone help me to solve the qn no. 29 of Tao Nan 2012 Prelims.

Thanks ksme. I could understand now from ur explanation

Thanks in advance

Hi,
Is this the ribbon question? If yes, here's the solution:

Vertical sides = 4*22cm = 88cm
top and bottom sides =2*(15+20)=70cm
Ribbon used to tie the bow = 200-88-70=42cm
Answer = 0.42m