Tutor MathsGuru: Ask me for your burning Maths questions!

[Hifive]

Hi Dharma


Thank you so much for your fast advice. Really appreciate your help.

[Dharma]

Hifive:

Hi Dharma


Thank you so much for your fast advice. Really appreciate your help.

No worries.

[Cheerfuldad]

Vanilla Cake:

Cheerfuldad:

Q1. Kailing and Jim had a total of $63. Kailing gave 0.3 of her share to Jim. Jim then gave 1/3 of the total amount of money he had to his brother. In the end, all the three children had the same amount of money. How much money did Kailing have at first?

Refer to http://www.onsponge.com/forum/35-thinkingmathonsponge/4321-p5-working-backwards.html.
This is a 5-mark question from Nanyang Primary School 2009 P5 CA2 paper 2 Q18.

Cheerfuldad:

Q2. A stack of bookmarks was shared among Peter, Tom and Jerry. Peter received 3 more than 50% of the bookmarks. Tom received 5 more than half of the remaining bookmarks. After Peter and Tom had taken their share. Jerry received 50% of the remainder and the last 3 bookmarks. What percentage of the stack of bookmarks did Jerry receive?

Refer to http://www.onsponge.com/forum/35-thinkingmathonsponge/4310-pr-5-remainder-concept.html#4325.
This is a 5-mark question from Nanyang Primary School 2009 P5 CA2 paper 2 Q17.

Cheerfuldad:

Q3. A dressmaker had some buttons. She used 1/7 of them on Monday and 1/11 of the remainder on Tuesday. On Wednesday, she bought 255 buttons and then had as many buttons as she had at first. How many buttons did she have at first?

6/7x10/11=60/77
17/77-> 255
77/77 -> 1155
Number of buttons that the dressmaker had at first = 1155.

This is a 4-mark question from Nanyang Primary School 2009 P5 CA2 paper 2 Q13.

Cheerfuldad:

Q4. A group of boys played only two types of sport during recess. 1/4 of them played badminton and 2/3 of them played football. 1/6 of the boys played both sports and 90 boys did not play any sports at all. How many boys were there?

1/4-1/6=1/12
2/3-1/6=1/2
1-1/12-1/2-1/6=1/4

1/4->90
4/4-> 90x4=360
Number of boys = 360

This is a 3-mark question from Nanyang Primary School 2009 P5 CA2 paper 2 Q6.

For the benefits of readers in this forum, it's good if you are able to state the source of your questions and given answers if available.This will help to save time for potential problem solvers rendering their help to your questions.
Thanks.

VC's mum

Hi VC's mum,

Thank you very much!

Cheers!

Cheerfuldad

[tianzhu]

Dharma:

I was thinking if 2 cuts of 36cm length spaced at 44cm are made perpendicular to the side of 47cm length leaving 1.5cm on either side. Then cut off the 44cm x 36cm x 24cm block from the original block and we are left with a U shaped block.
Really need Tianzhu’s help me on the illustration so that we can visualize better. This may gives a different total area.

Hi Dharma

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4133/4950916508_849577cebf_b.jpg\">

[Dharma]

tianzhu:

Dharma:

I was thinking if 2 cuts of 36cm length spaced at 44cm are made perpendicular to the side of 47cm length leaving 1.5cm on either side. Then cut off the 44cm x 36cm x 24cm block from the original block and we are left with a U shaped block.
Really need Tianzhu’s help me on the illustration so that we can visualize better. This may gives a different total area.

Hi Dharma

Hope this helps.

Best wishes

http://farm5.static.flickr.com/4133/4950916508_849577cebf_b.jpg\">

Thanks Tianzhu. There is 1 more shape that will look like a rectangular hollow section with 1.5cm thickness on 2 sides and 1 thickness on the other 2 sides. Don't bother to draw it out. My guess is all 3 shapes will give different total areas.

[tianzhu]

Dharma:

Thanks Tianzhu. There is 1 more shape that will look like a rectangular hollow section with 1.5cm thickness on 2 sides and 1 thickness on the other 2 sides. Don't bother to draw it out. My guess is all 3 shapes will give different total areas.

Hi Dharma

Yes, how one cuts out the block (44*36*24) affects the surface area of the remaining block.

I am not sure if the question from the TS is reproduced exactly from the source or it has been summarised. How the question is worded has direct bearing on the answer.

If how the block is cut out is not expressly worded in the question, then one should go for the L shaped remainder which is easier to calculate the surface area.

Best wishes

[ganchiong]

Hi


To all the Maths Guru, appreciate if you could enlighten me on the following question.

The following question is taken from CHIJ St Nicholas 2009 P2 Q15:

A bullet train took 5 hrs to travel from P to H while an electric train took 4 hrs longer to travel from H to P. Both trains set off at the same time and moved towards each other. 2 hours later, they were 255 km apart. What was the speed of the electric train?

Thank you.

[tianzhu]

ganchiong:

The following question is taken from CHIJ St Nicholas 2009 P2 Q15:

A bullet train took 5 hrs to travel from P to H while an electric train took 4 hrs longer to travel from H to P. Both trains set off at the same time and moved towards each other. 2 hours later, they were 255 km apart. What was the speed of the electric train?

Hi
Hope this helps.

For bullet train, it took 5 hours to cover the journey.
So for 1 hour the bullet train will travel 1/5 of the journey

For electric train, it took 9 hours to cover the journey.
So for 1 hour the bullet train will travel 1/9 of the journey

Find the lowest common multiple of 5 and 9 which is 45.

Bullet train
9 units ----1 h
18 units ------2 h

Electric train
5 units ----1 h
10 units ------2 h

45 - 28 ------ 17

17 units ----- 255
1 unit ----- 15 km

Total distance ------ 45 units ----- 45 x 15 ------ 675 km

Speed of electric train -------675/9 -------75km/h

Best wishes

[ganchiong]

tianzhu:

ganchiong:

The following question is taken from CHIJ St Nicholas 2009 P2 Q15:

A bullet train took 5 hrs to travel from P to H while an electric train took 4 hrs longer to travel from H to P. Both trains set off at the same time and moved towards each other. 2 hours later, they were 255 km apart. What was the speed of the electric train?

Hi
Hope this helps.

For bullet train, it took 5 hours to cover the journey.
So for 1 hour the bullet train will travel 1/5 of the journey

For electric train, it took 9 hours to cover the journey.
So for 1 hour the bullet train will travel 1/9 of the journey

Find the lowest common multiple of 5 and 9 which is 45.

Bullet train
9 units ----1 h
18 units ------2 h

Electric train
5 units ----1 h
10 units ------2 h

45 - 28 ------ 17

17 units ----- 255
1 unit ----- 15 km

Total distance ------ 45 units ----- 45 x 15 ------ 675 km

Speed of electric train -------675/9 -------75km/h

Best wishes

Hi Tianzhu,

Thank you very much!

Cheers!

[acehkr3009]

Hi all,


I have a question here and my solution, but not too sure if method is appropriate for Pri level and if answer is correct. Need some feedback.

1/3 of the flowers in a park were Roses and the rest Hibiscus. 3/4 of the Roses were pink and the rest were red. 5/8 of the Hibiscus were red and the rest were pink. There were 156 pink flowers. How many flowers were there in the park?

1/3 Roses, 2/3 Hibiscus
3/4 of Roses are pink & 3/8 ( 1 - 5/8 ) of Hibiscus are pink

Fraction of pink Roses -> 1/3 x 3/4 = 1/4
Fraction of pink Hibiscus -> 2/3 x 3/8 = 1/4

Fraction of pink flowers -> 1/4 + 1/4 = 1/2

If 1/2 -> 156
2/2 -> 2 x 156 = 212

Total there is 212 flowers in the park