Q&A - PSLE Math

[Zack7]

Chenonceau:

My Question 1

http://i39.tinypic.com/e5jibm.png\">
http://i42.tinypic.com/2v7v6s8.jpg\">

Please help... Thank you.

wow kids these days learn crazy stuff... i learn these in secondary sch IIRC....


anyway

total volume of bottle = 6x6x32 + 18x12x12 = 3744

volume of 7/8 filled with water = 7/8 x 3744 = 3276

volume of water in the top cuboid = 3276 - 18x12x12 = 684

height of water level in the top cuboid = 684/36 = 19

height from the base of the bottle = 19 + 18 = 37cm

[peggy]

Hi Tianzhu,


The questions were shared with me by a friend’s DD enrichment class.

[tianzhu]

Chenonceau:

My Question 1

http://i39.tinypic.com/e5jibm.png\">
http://i42.tinypic.com/2v7v6s8.jpg\">

Please help... Thank you.

Hi

Where is this question from? It’s quite an interesting one.

Consider first the bigger cuboid of 12cm by 12 cm base and height 18cm.

Picture this,it is made up of 4 number of cuboid of 6cm by 6cm and height 18cm.

Total volume of water (8/8 or 8 units) --------- 5 number of cuboid of 6cm by 6cm and height 18cm plus one cuboid of 6cm by 6cm and height 14cm (18+14=32)

8 units ------ (5*18) + 14 ------ 104
7 units ------- 91

91 – 72 ------- 19

Water level from base of bottle ------- 18+19 ------- 37

Best wishes

[tianzhu]

Bunny27:

1. At a carnival, 30% of the people are adults, 20% are girls and the rest are boys. After some adults have left, the percentage of adults at the carnival becomes 20%. How many adults have left the carnival?

Hi

Please check your question.

I think some information might be missing.

Best wishes

[Zack7]

[quote]


Hi, can someone help on this question:

1. At a carnival, 30% of the people are adults, 20% are girls and the rest are boys. After some adults have left, the percentage of adults at the carnival becomes 20%. How many adults have left the carnival?

:thankyou:[/quote]this question seems incomplete?

anyway

let x be total number of people before leaving adults (OLD total)
let y be total number of people after leaving adults (NEW total)
let c be number of adults leaving

you will get 3 simultaneous equations based on the information of the question

x-c = y
0.3x - c = 0.2y
0.7x = 0.8y

so

0.3 (y+c) - c = 0.2y
y = 7c
x = 8c

so the number of adults leaving is c = x/8 or y/7

the question doesn't give an absolute number, only percentages, so the number of people leaving can only be expressed as a percentage.

[Essential]

Please help my boy with the below question:-


Adam , Benjamin and carina had a total of $845. They went shopping and Adam spent 30% of his share, Benjamin spent $100 and Carina spent twice as much as Adam spent. Given that the three of them had $385 left, how much money did Benjamin and Carina have altogether at first?

[tianzhu]

Essential:

Please help my boy with the below question:-


Adam , Benjamin and carina had a total of $845. They went shopping and Adam spent 30% of his share, Benjamin spent $100 and Carina spent twice as much as Adam spent. Given that the three of them had $385 left, how much money did Benjamin and Carina have altogether at first?

Hi

You may use MD.

spent
Adam ----- 3 units
Carina ------ 6 units
Benjamin ------ 100

845 – 385 ------ 460

9 units + 100 ------- 460
1 unit ------ 40

Adam ------- 10 units ------- 400 (Adam’s money at first)

845 – 400 ------ 445 (Amount Benjamin and Carina had altogether at first)

Best wishes

[Essential]

tianzhu:

Essential:

Please help my boy with the below question:-


Adam , Benjamin and carina had a total of $845. They went shopping and Adam spent 30% of his share, Benjamin spent $100 and Carina spent twice as much as Adam spent. Given that the three of them had $385 left, how much money did Benjamin and Carina have altogether at first?

Hi

You may use MD.

spent
Adam ----- 3 units
Carina ------ 6 units
Benjamin ------ 100

845 – 385 ------ 460

9 units + 100 ------- 460
1 unit ------ 40

Adam ------- 10 units ------- 400 (Adam’s money at first)

845 – 400 ------ 445 (Amount Benjamin and Carina had altogether at first)

Best wishes

Thanks Tianzhu. Always trouble u pei sei

[peggy]

Tianzhu,


Thanks for solving my speed questions.

[tianzhu]

Essential:

Thanks Tianzhu. Always trouble u pei sei

Hi

Good Morning.

You're welcome.

Best wishes