Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

keborah:

Hi Mathsguru,


Needs you help here:
Faridah had 30 mini chocolat bars. She shared them equally among 2 girls and 3 boys. How many mini chocolate bars did each child receive?

My question is whether Faridah is considered as one of the 2 girls or not?

Many thanks,
Keborah

Hi Keborah,

Since the question is phrased in this way (\"shared equally among\"), Faridah is not considered as one of the girls. Like what CoffeeCat said, if Faridah is included, it will be \"shared with 2 girls...\".

Hope this clarifies!


MathsGuru

[mathsguru]

firebird:

Dear mathsguru


Good evening

Please help me on the following maths:

1) The ratio of the number of pencils to the number of rasers in a box was 2:3. When 42 pencils were added and 15 erasers were removed, the ratio of the number of pencils to erasers became 3:4. How many erasers were there left in the box? Answer given was 624.

2) Container A has 150 more marbles than Container B. If 30 marbles are being transferred from Container B to Container A, there will be thrice as many marbles in Container A as Container B. How many marbles are there in Container A in the begining? Ansewr given 285.

3) 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 5 times the number of black marbles left.
How many marbles are there in the bag? Amswer given 475.

Many thanks
firebird

Hi Firebird,

Here're my solutions.


MathsGuru

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

http://www.postimage.org/image.php?v=aVtGF9r

http://www.postimage.org/image.php?v=aVtGAa9

[mathsguru]

YLH88:

Hi Mathsguru,


Need your help with the below 2 questions :

1) Jane was thinking of a fraction. The sum of its numerator and denominator was 34. After I added 98 to its denominator, the fraction became 1/11. What was the fraction that Jane was thinking of ?
(ans given was : 11/23)

2) Alex, Ben and David went for a run but none of them completed the run.
Ben ran 5 times as far as Alex before he stopped.
David stopped 1 km before the finishing line and he ran 3 km less than twice the distance Ben ran.
The three of them ran 21 km, how long was the run ?
(ans given was 13 km)

Thank you so much!!

Hi YLH88,

Here're my solutions.


MathsGuru

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

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

[mathsguru]

firebird:

Dear Mathsguru


Good afernoon.

Please help if you have access to the quesions mentioned bellow.

I am rather in an unusual position. The reason being I have problems with 2 questions that have diagrams as part of the question. Which I am unable to attach herewith as I do not have a scanner. All the these questions are from S'pore Hokkien Kuay Kuan, 2009, Primary 6, Paper 2, Preliminary Examination:

Question 11) In the figure below, not drawn to scale, PQRS is a rectangle with a length of 45 cm and a width of 22 cm. The area of te TUVW is 75 cm2. Find the ratio of the shaded area to the unshaded area.


Quesion 13) The figure below shows 2 squares, ABCD and EFGH, The length of each square is a whole number. The area of the unsaded part is 28 cm2. What is the perimeter of the square ABCD?

Question 15) A car and a coach travelled from Town A to Town B. The coach left town A at 0648 and it took 5 hours to reach Town B. The car started 30 minutes later than the coach and it took 4 hours to reach Town B. At what time did the car catch up with the coach?

Please help me if you have access to the question above.

Many thanks
firebird

Hi Firebird,

Here're my solutions!


MathsGuru

http://www.postimage.org/image.php?v=aVtOiz0

http://www.postimage.org/image.php?v=aVtOl39

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

[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 ?

[firebird]

Dear Vanilla cake and Mathsguru


Good morning.

Many thanks for solving the maths posted by me.
firebird

[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

[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

[Vanilla Cake]

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,
You are welcome!

From the question itself, it stated that David stopped 1 km before the finishing line and he ran 3 km less than twice the distance Ben ran.

We know that Ben had run 5 units from Ben ran 5 times as far as Alex before he stopped.
So, David ran 5 units x 2 = 10 units minus 3 km. But he stopped 1 km before the finishing line, therefore the length of the run must be 10 units minus 3 km + 1 km.

From the earlier calculation, 1 unit has been worked out to be 1.5 km.
10 units - 3 km + 1 km
= 10(1.5) km - 3 km + 1 km
= (15-3+1) = 13 km which was the length of the run.

[Vanilla Cake]

Hi firebird,


All your questions are from http://www.orlesson.org/orp/09Ma/2009-P6-Math-SA2-SCGS.pdf and some of them have been answered by Uncle Observer. Pls refer to them while waiting for Mathsguru's solutions.

firebird:

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 from Singapore Chinese Girls' School Paper 1 Q15. Four answer options are given for this question. Option (1) 40 min, Option (2) 50 min, Option (3) 60 min and Option (4) 100 min

Fixed Distance or constant distance or common distance
Ratio of speed
Pt A to Pt B : Pt B to Pt A
30 : 20
3 : 2

Ratio of speed is inversely proportional to the ratio of time

Ratio of time
Pt A to Pt B : Pt B to Pt A
2 : 3

Time time taken to complete the race was 1 h 40 min = (60+40) min = 100 min. Total time (ratio) in terms of units = 2+3 = 5.

5 units = 100 min
1 unit = 20 min

From Point B to Point A, it took Alan 3 units = (3 x 20) min = 60 min which is Option (3).

firebird:

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.

This is a 3-mark question from paper 2 - Q6 from the same paper.
Using ratio to solve.
Before
C : D
4 : 7
Multiply both sides by 4
16 : 28

Change
Each of them spends $28.

After
C : D
3 : 7
Multiply both sides by 3
9 : 21

Note that the difference for Colin = (16-9) = 7 units and
the difference for Daniel = (28-21) = 7 units
meaning that both difference are equal as they spend equal amount of money.

7 units = $28
Now, Colin has 9 units means 28/7x9 = $36

firebird:

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?

This is a 4-mark question from paper 2 - Q14 from the same paper.
Pls refer to http://2.bp.blogspot.com/_NGNaLTzN5_U/SrIXzZccQLI/AAAAAAAADqk/8w0na5ziEss/s1600-h/Maths0609SA2P2SCGSRatioQ14A.JPG.

firebird:

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?

This is a 4-mark question from paper 2 - Q15 from the same paper.
Pls refer to http://4.bp.blogspot.com/_NGNaLTzN5_U/SrG9JlyKltI/AAAAAAAADps/RwzFeaqu_D8/s1600-h/Maths0609SA2P2SCGSFractionQ15A.JPG.

firebird:

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?

This is a 5-mark question from paper 2 - Q17 from the same paper.
Pls refer to http://1.bp.blogspot.com/_NGNaLTzN5_U/SrG8lTC896I/AAAAAAAADpU/avMk0Drfs9k/s1600-h/Maths0609SA2P2SCGSRatesQ17A.JPG.

firebird:

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.

This is a 5-mark question from paper 2 - Q16 from the same paper.
Pls refer to http://1.bp.blogspot.com/_NGNaLTzN5_U/SrMyBXxSdlI/AAAAAAAADuE/NikqH4qQHjs/s1600-h/Maths0609SA2P2SCGSCircleQ16A.JPG.