Tutor MathsGuru: Ask me for your burning Maths questions!

[Dharma]

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!

Q1)

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


Q2)

12.5% of A is shaded
20% of C is shaded
5% of B is shaded

100% of A + 100% of C = 30% of B -------------(1)
12.5% of A + 20% of C = 5% of B ------------------(2)

75% of A + 120% of C = 30% of B ………………..(3) = (2) X 6

100% of A + 100% of C = 75% of A + 120% of C
25% of A = 20% of C
A = 80% of C

[Dharma]

maths6a:

Is the answer 77 or 78 1/3? Which is more acceptable? Thanks....... :?:


Apparently answer from schoolS' teacherS is 77. THanks.
Oh when I use 77 to workbacks, base and height don't tally.
When I use 78 1/3, they are ok.

Who that clever person who knows to change 94 to 90?

That was what I have been told to do. But I just want to know what should the answer be if it's 94. thanks, very stubborn me.

Hi maths6a,

The area of rect ABCD cannot be 94cm2. See below

http://www.postimage.org/image.php?v=aVAo6QJ

[maths6a]

ok. Thanks for taking time to clarify.

[Dharma]

maths6a:

ok. Thanks for taking time to clarify.

No worries

[firebird]

Dear Dharma


Thank you very much.

With best regards
firebird

[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 !