Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

OngMum:

Hi Mathsguru,


I have two questions that need your gudiance:

1. The figure below is made up of 4 squares and a rectangle. Rectangle ABCD has a perimeter of 40cm. The total area of the 4 squares is 500cm2. Find the area of the rectangle.

http://www.postimage.org/image.php?v=gxKXsSS

2. The figure below, not drawn to scale, shows three triangles of differnet sizes overlapping one another. The sum of areas of Triangle A and Triangle C is 30% that of Triangle B. 12.5% of Triangle A is shaded, 5% of B is shaded and 20% of Triangle C is shaded. Express the area of Triangle A as a percentage of the area of Triangle C.

http://www.postimage.org/image.php?v=gxKY8hi

Thank you! Cheers!

Dear OngMum,

Please see my solutions as attached below. Hope they help!


MathsGuru

http://www.postimage.org/image.php?v=Tsk1jj9

http://www.postimage.org/image.php?v=Tsk1oir

[Dharma]

firebird:

Dear Dharma


Thank you very much.

With best regards
firebird

My pleasure.

[CJM]

Some trees are planted along a 400 metres road with a tree on each end of the road. The distance between every 2 nearest trees are 4 metres. If the distance between every 2 nearest trees is to be changed to 5 metres, how many trees will not be removed?

[Yu Xuan]

CJM:

Some trees are planted along a 400 metres road with a tree on each end of the road. The distance between every 2 nearest trees are 4 metres. If the distance between every 2 nearest trees is to be changed to 5 metres, how many trees will not be removed?

Multiple of 4 that has a '0' in the ones place are...

20, 40, 60, 80, 100, 120, ... (20 in total)

20+1 = 21

Is that the answer?

[CJM]

Yu Xuan:

CJM:

Some trees are planted along a 400 metres road with a tree on each end of the road. The distance between every 2 nearest trees are 4 metres. If the distance between every 2 nearest trees is to be changed to 5 metres, how many trees will not be removed?

400 / 4 = 100
100 + 1 = 101

400 / 5 = 80
80 + 1 = 81

101 - 81 = 20

Is that the answer?

the teacher has not posted the answer yet : )
thanks for ur help !

[maths6a]

i also calculated 20. all the trees that were planted on mulitples of 5 and 10, in this case are the ones on 20m, 40m,… and 20 tress need not be removed.

[CJM]

maths6a:

i also calculated 20. all the trees that were planted on mulitples of 5 and 10, in this case are the ones on 20m, 40m,... and 20 tress did not be removed.

thank u : )

[Yu Xuan]

I think I cause some confusion, my first working is wrong... I realised it after reading it again. I have edited my answer and hence my answer is 21 instead after adding the first tree.


Sori abt that :lol:

[Tang]

Yu Xuan:

CJM:

Some trees are planted along a 400 metres road with a tree on each end of the road. The distance between every 2 nearest trees are 4 metres. If the distance between every 2 nearest trees is to be changed to 5 metres, how many trees will not be removed?

Multiple of 4 that has a '0' in the ones place are... It is multiple of both 4 and 5, ie 20.

20, 40, 60, 80, 100, 120, ... (20 in total)

20+1 = 21

Is that the answer?

Hi,

4 x 5 = 20

400 / 20 = 20

20 + 1 = 21 trees will not be removed.

[Tang]

CJM:

maths6a:

i also calculated 20. all the trees that were planted on mulitples of 5 and 10, in this case are the ones on 20m, 40m,... and 20 tress did not be removed.

thank u : )

Hi,

Don't forget to add the one at '0'.