Tutor MathsGuru: Ask me for your burning Maths questions!

[tianzhu]

Publica:

2. Two candles of the same height are lit at the same time. The first is consumed in 4 hours, the second in 3 hours. Assuming that each candle burns at a constant rate, how many hours after being lit was the height of the first candle twice the height of the second?

Hi

Please follow this link.It may help to solve your question.
http://www.kiasuparents.com/kiasu/forum/viewtopic.php?t=280&start=1530

Best wishes

[Publica]

Hi Tianzhu,


Many thanks for sending the link to the detailed illustration.

Regards
Publica

[tianzhu]

Hi Publica


When using the heuristic Work backwards, starts with the end results and reverses the steps you need to get those results. You may work it out using MD or Units Method (in the form of a tabulated list).

Well, if I could reverse the steps I’ve taken in my life journey, would I do it differently? Sad to say, not everything in life can be reversed in a systematic way.

Enjoy the PSLE journey with your kid.

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4079/4904629134_b8a20ecd0f_b.jpg\">

[kwcllf]

Hi,


Please help with the following question:

Andy, Benny and Calvin have 150 buttons altogether.
If Andy gives 3/7 of his buttons to Benny and Benny gives 32 buttons to Calvin and Calvin gives 26 buttons to Andy, they have the same number of buttons.

How many buttons do they have at first?

(I got the answers as Andy=42, Benny=64 and Calvin=44 by using algebra. But I am afraid my P4 son may not understand. Hope someone can help with an alternative solution).

Thanks!

[livewith_vanilla]

kwcllf:

Hi,


Please help with the following question:

Andy, Benny and Calvin have 150 buttons altogether.
If Andy gives 3/7 of his buttons to Benny and Benny gives 32 buttons to Calvin and Calvin gives 26 buttons to Andy, they have the same number of buttons.

How many buttons do they have at first?

(I got the answers as Andy=42, Benny=64 and Calvin=44 by using algebra. But I am afraid my P4 son may not understand. Hope someone can help with an alternative solution).
Thanks!

Since the three boys give each other and not give away, the TOTAL number of marbles stay the same(eg. 150)

Hence, 150/3=50

Thus each boy has the same number of marbles left.

Andy:

Calvin gives Andy 26 marbles.

Thus, 50-26=24

In the first place, Andy gave Benny 3/7 of his marbles, before Calvin gave him any marbles.

Thus, Andy has (1-3/7=4/7) marbles left.

4u->24
1u->24/4=6
7u->6x7=42

Benny:
Andy gave 3u of his marbles to Benny.

Thus,

1u(of Andy)->6
3u(of Andy)->6x3=18

Andy gave Benny 18 marbles.

50+32=82

This is the number of marbles Benny would have if he did not give Calvin any marbles.

However, since Andy gave Benny some marbles, we have to substract 18 marbles from 82 marbles.

82-18=64

Benny has 64 marbles.

Calvin:

The Long Way:

Since Calvin gave Andy 26 marbles,

50+26=76

Calvin would have 76 marbles if he did not give any marbles to Andy.

However, Benny gave Calvin 32 marbles.

Thus,

76-32=44

Calvin would have 44 marbles.


Short way:

Since we found out Andy has 42 marbles and Benny has 64 marbles, we just need to take the total marbles subtract the sum of Andy's and Benny's marbles.

42+64=106
150-106=44

Calvin would have 44 marbles.

[beauty queen]

Dear MathsGuru please help me with these questions,


1) Container A contains 250 red marbles and 200 blue marbles. Container B contains 600 red marbles and 150 blue marbles.How many red and blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in container B are red.

2)There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.

Please help

[super star]

please help me with this problem

Tank p with 40cm by 30cm base is filled with water till it reaches the height 55cm .water was then poured from tank p to tank q with base 100cmby20cm, untill the height of the water level in tank p became twice that of the water level in tank q.find the volume of water in tank q. give your ans in liters.

[livewith_vanilla]

beauty queen:

Dear MathsGuru please help me with these questions,


1) Container A contains 250 red marbles and 200 blue marbles. Container B contains 600 red marbles and 150 blue marbles.How many red and blue marbles must be moved from Container A to Container B such that 25% of the marbles in Container A are red and 75% of the marbles in container B are red.

2)There are some black and white marbles in a bag. If 20 black marbles are removed from the bag, the total number of marbles left will be 7 times the number of black marbles left. If 50 white marbles are removed from the bag, the total number of marbles left will be 5 times the number of black marbles left. How many marbles are there in the bag.


Hi your questions from ACS Maths Prelim paper right?

Please refer to here:

http://www.kiasuparents.com/kiasu/content/some-math-questions-and-answers
Please help

[starlight1968sg]

super star:

please help me with this problem

Tank p with 40cm by 30cm base is filled with water till it reaches the height 55cm (as per the picture given the tank is taller than 55cm) .water was then poured from tank p to tank q with base 100cmby20cm, untill the height of the water level in tank p became twice that of the water level in tank q.find the volume of water in tank q. give your ans in liters.

What is the ans?

I dont really understand the sentence:
\"untill the height of the water level in tank p became twice that of the water level in tank q\"

Volume of water in tank p = 40*30*55= 66 litres.
Volume of water in tank q = 100*20*(55/2) = 55 litres.

[livewith_vanilla]

super star:

please help me with this problem

Tank p with 40cm by 30cm base is filled with water till it reaches the height 55cm .water was then poured from tank p to tank q with base 100cmby20cm, untill the height of the water level in tank p became twice that of the water level in tank q.find the volume of water in tank q. give your ans in liters.

55x40x30=66000

40x30=1200
100x20=12000
12000+1200=13200
66000/13200=5
5x2=10
10x100x20=20000

20000cm3 = 20L

Ans:20L

others please double confirm answer.