Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

YLH88:

Hi Mathsguru, Vanilla Cake,


Thanks for the solution!

For the 2nd qn on the distance run, why is the total distance 10u - 3km + 1km and not 10u + 1km since David stopped 1 km before the finishing line ?

Hi YLH88,

The total distance David ran was 3km short of twice Ben's distance (5units x 2). Hence, 10units - 3km = 12km is what David ran. Since he stopped 1km before the finishing line, the total distance is 12km + 1km = 13km.

Hope this clarifies...

Cheers,
MathsGuru

[YLH88]

Hi Mathsguru, Vanilla Cake,


OIC... Thank you! Now I understand

Sorry, 1 more question below need your expertise advise. :?
This question is from St Nich SA1 Paper 2 Qn 12 :

The figure below is made up of 2 squares and a rectangle. The ratio of the area of A to the area of B to the area of C is 9 : 4 :3.
The ratio of the unshaded part of B to the unshaded part of C is 4 : 1.
If the shaded part is 56 m sq, find the area of A that is not covered by B.
(ans is 105 cm sq)

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

Thank you very much!

[CoffeeCat]

YLH88:

Hi Mathsguru, Vanilla Cake,


OIC... Thank you! Now I understand

Sorry, 1 more question below need your expertise advise. :?
This question is from St Nich SA1 Paper 2 Qn 12 :

The figure below is made up of 2 squares and a rectangle. The ratio of the area of A to the area of B to the area of C is 9 : 4 :3.
The ratio of the unshaded part of B to the unshaded part of C is 4 : 1.
If the shaded part is 56 m sq, find the area of A that is not covered by B.
(ans is 105 cm sq)

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

Thank you very much!

In ratio stuff like constant difference or constant total are crucial.

Area of
A:__B : __C : Difference between B & C : unshaded B : unshaded C
9: ___4 : 3 :________________1
___________________________3 : 4 : 1
27: 12 : 9 :_________________3 : 4 : 1

(pardon the underscores they are used for alignment)
from this we know that
the shaded portion of B = 12-4 = 8 units which correspond to 56m^2
therefore difference between A & B is (27-12) * 7

[mathsguru]

firebird:

Dear Mathsguru


Good morning.

Kindly help me on the following maths:
1) Alan completed a race in 1 hour 40 minutes. In the race, he ran at an average speed of 30 m/min from Point A to Point B and then ran back to from Point B to Point A at an average speed of 20 m/min. How long did he take to run back to Point A from Point B.

This is a 2 mark question. Given answer 60 minutes. But I really do not know!

2)The ratio of the amount of money Colin has to the amount of money Daniel has is 4:7. After each of them spends $28, their ratio becomes 3:7.
Find the amount of money Colin has now. Given answer $36.

3) Mrs Lim bought some forks and spoons in the ratio of 4:3. Each spoon cost 50 cents more than each fork. If she spends $156 altogether and the amount she spent on the fork was $12 more than the amount she spent on spoons. How many forks and spoons did she buy?
Given answer 42.

4) Mr Tan had 130 durians and mangosteens. After he sold 2/3 of the durians and 2/5 of the mangosteens, he had 36 more mangosteens than durians left. How many fruits had he left in all?
Given answer 66.

5) Ahmad and Halim together took 5 days to paint their house. If Ahamad and Halim work together for 2 days, followed by Ahamad working alone for 8 days, Halim will take 1 more day to complete the ramaining work. How long will Ahamad take to paint the house all by himself?

Given answer 17 1/2 days

6) The figure below is made up of a circle, a triangle and two identical semi-circles. The diameter of the semi-circle is 4 cm. Find the area of the shaded regions.

I apologise for not inserting the diagram here. Kindly, help me. The question is from S'pore Girls School Preliminary Exam 2009 Question number 16 paper 2.

Given answer 30.8cm2. I really do not know were to start for this question.

Very sorry for the inconveience casused.

Reagrds
firebird

Hi Firebird,

Here're my solutions. Hope they are clear enough!


MathsGuru

http://www.postimage.org/image.php?v=gx7MMx0

http://www.postimage.org/image.php?v=gx7MP19

http://www.postimage.org/image.php?v=gx7MRwi

http://www.postimage.org/image.php?v=gx7MU0r

http://www.postimage.org/image.php?v=gx7MWvA

http://www.postimage.org/image.php?v=gx7MY_J

[mathsguru]

firebird:

Dear mathsguru


Please help me on this maths, which i have forgot to post earlier:

1) Tracy counted the number of 10cents coins, 20 cents coins ans 50 cents coins in her piggy bank. The number of 10cents coins was 24 more than the number of 50 cents coins. After spending 3/5 of the 10cents coins, 1/4 of the 20 cents coins and 18 50cents coins, she had equal number of 10cents coins and 20 cents coins. The number of 50 cents coins now formed 40% of the remaining number of coins.

a) How many 10 cents coins did tracy have at first? Given ans 90
b) How much did she spend in all? given ans $16.80

Many thanks
firebird

Hi Firebird,

Here's my solution.

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=gx7NJor

[mathsguru]

YLH88:

Hi Mathsguru, Vanilla Cake,


OIC... Thank you! Now I understand

Sorry, 1 more question below need your expertise advise. :?
This question is from St Nich SA1 Paper 2 Qn 12 :

The figure below is made up of 2 squares and a rectangle. The ratio of the area of A to the area of B to the area of C is 9 : 4 :3.
The ratio of the unshaded part of B to the unshaded part of C is 4 : 1.
If the shaded part is 56 m sq, find the area of A that is not covered by B.
(ans is 105 cm sq)

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

Thank you very much!

Hi YLH88,

You're most welcome. Glad you understand it!

Here's the solution!


MathsGuru

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

[starlight1968sg]

Hi,

I need some help again.

1) Andy, Betty, Candy and Danny each have some money. The amount of money Andy has is 1/3 of the total amount of money Betty, Candy and Danny have. The amount of money Betty has is 1/4 of the total amount of money Andy, Candy and Danny have. The amount of money Candy has is 1/5 of the total amount of money Andy, Betty and Danny have. If Danny has $1725, how much do they have altogether?

2) Tom and Jerry each has some money. If Tom spends $90 per day and Jerry spends $45 per day, Tom will have $1100 left when Jerry has spent all his money. If Tom spends $45 each day and Jerry spends $90 each day, Tom will have $1700 left when Jerry has spent all his money. How much did Jerry have?

I am totally clueless on how to start?

MTIA.

[Vanilla Cake]

starlight1968sg:

1) Andy, Betty, Candy and Danny each have some money. The amount of money Andy has is 1/3 of the total amount of money Betty, Candy and Danny have. The amount of money Betty has is 1/4 of the total amount of money Andy, Candy and Danny have. The amount of money Candy has is 1/5 of the total amount of money Andy, Betty and Danny have. If Danny has $1725, how much do they have altogether?

The amount of money Andy has is 1/3 of the total amount of money Betty, Candy and Danny means total $ in terms of ratio is 1+3=4.

The amount of money Betty has is 1/4 of the total amount of money Andy, Candy and Danny have means total $ in terms of ratio is 1+4=5.
The amount of money Candy has is 1/5 of the total amount of money Andy, Betty and Danny have means total $ in terms of ratio is 1+5=6.

LCM for 4,5,6 is 60.

A : B+C+D
1 : 3
15:45

B : A+C+D
1 : 4
12 : 48

C : A+B+D
1 : 5
10 : 50

D->(60-15-12-10) units=23 units

23 units = $1725
60 units = $4500
Total amount of money that they have altogether is $4500

starlight1968sg:

2) Tom and Jerry each has some money. If Tom spends $90 per day and Jerry spends $45 per day, Tom will have $1100 left when Jerry has spent all his money. If Tom spends $45 each day and Jerry spends $90 each day, Tom will have $1700 left when Jerry has spent all his money. How much did Jerry have?

Pls refer to this similar question from ACS(J)/ACS(P)2008 P6 Prelim Q41.Here's the http://prischoolmaths.blogspot.com/2009/06/maths-whole-number_7545.html. You should be able to figure it out and solve accordingly.
Hope the above clues are enough for you to start solving them while waiting for Mathsguru's solutions.

[firebird]

Dear mathsguru


Good evening.

Thank you very much for your answers. All of them are very clear.

With best regards
firebird

[ChiefKiasu]

mathsguru, just as a small token of our appreciation for the help you have rendered to our community, we award you 5000 KPs for you kind contributions!