Tutor MathsGuru: Ask me for your burning Maths questions!

[Almighty]

Dharma:

Hi Almighty,


For the NMOS 2010 qn, your method of finding the average speed for Tom and Harry for a block of 12 mins and 19 mins will not be so appropriate foe this question because we will not be able to know exactly whether they meet each other when Tom is running or walking if we use your method of finding the average speed for each block of time.

By listing you will know that after 38 mins, they are 1650m apart snd then everything is so straightforward. (u also know both are running at that time)

BTW ... My advise is for you to concentrate more on PSLE type qns as the skills required to solve to solve Olympiad questions will be bit different from
what is required of child who is attempting to solve PSLE problem sums.

Thank you very much Dharma sir.

[Dharma]

ck123:

Hi all


How to draw model for this question?

Ali, Bala, Clyde and Dingyi shared a box of pens. Ali received 20% of the total number of pens which Bala, Clyde and Dingyi received altogether. Bala received 50% of the total number of pens which Ali, Clyde and Dingyi received altogther. Clyde received 80% of the total number of pens which Ali, Bala and Dingyi received altogether. Dinyi received 6 pens. How many pens were in the box at first?

Ans: 108

Thanks

Sorry, below is not a Model Method solution.

Ali => 1/6 = 3/18
Bala => 1/3 = 6/18
Clyde => 4/9 = 8/18

Dingyi = 1 - 3/18 - 6/18 - 8/18 = 17/18
1u = 6
Total no of pens = 18u = 18 x 6 = 108

[Almighty]

Vanilla Cake:

Almighty:

Mrs Lee was 44 years old.Her son was twice her daugther's age.Mrs Lee will be twice her son's age when her daugther is 26 years old.How old will Mrs Lee be when her daughter is 20 years old?

Assume daughter's age to be N.
Mrs Lee's age: 44 years old
Daughter's age: N years old
Son's age : 2N years old

Difference between daughter's age and son's age = N years old

Mrs Lee's age: (52+2N) years old
Daughter's age: 26 years old
Son's age: (26+N) years old

Difference in the age between Mrs Lee and her son is the same.
44-2N = (52+2N)-(26+N)
44-2N=26+N
3N=18
N=6

When daughter is 20 years old, Mrs Lee's age = (52+2N)-6 = (52+12)-6=58 years old

Pls advise the source of this question as this question is almost the same as the 5-mark http://www.wendykoh.com/07/primary6-scgs-maths.pdf from Singapore Chinese Girls' School (Primary) 2007 P6 Prelim.

Hi Vc,
Sorry , i dont remember from which forum i took this qt. All tricky qts i used to put in my Xel sheet and try to solve them when i get time. So, i dont exactly remember from which website i took this qt.Thanks 4 yr timely help.

[Vanilla Cake]

2DMommy:

In a box, there are yellow, red and green beads, 1/3 of the beads in the box are yellow. There are 30 more red beads than yellow beads. The rest of the 15 beads are green. How many beads are there altogether?

Hi 2DMommy,
Pls advise the source of your question so that we (KSP members) know the level of this question in order to apply the appropriate method to solve.
Not sure whether this method is suitable or not?

Yellow: u
Red: u+30
Green: 15

Total number of beads = 3u.
Number of green beads = 3u-u-(u+30)=3u-u-u-30 = u-30

u-30=15
u=45
3u= 3x45=135

Number of beads altogether = 135

If this is really a P3 question then model solutions are easy to understand than the above method. Pls kindly wait for other KSP members to post their model solutions.

[wkong]

Thanks VC for your help.



Another 1 more question that needs help:

The figure is not drawn to scale. It shows a rectangle divided into 6 parts. Each part has a different area.

a) Find the total area of P and Q.

b) Find the perimeter of the figure.



http://www.postimage.org/

[YLH88]

Hi all,


Need help in the below question :

Sam and Harry started running at the same time from the opposite ends of the diameter of a circular track.
Both of them were running in the clockwise direction.
Sam took 12 minutes to run round the track once while Harry took 15 minutes to do the same.
How long did Sam take to run past Harry for the first time ?
(ans : 30 minutes)

http://postimage.org/image/1z70q6hqc/

Thank you!

[capricorn28]

Hi iFruit


Thank you for the clear explanation.

Best regards
Capricorn28

[capricorn28]

Hi All,


Need help on Catholic High School P5 SA2 - Year 2009
Paper 2 - Q6 and the ans is 16 degrees
Paper 2 - Q8 and the ans is 72%
Paper 2- Q13 and the ans is 80cm
Paper 2 - Q14 and the ans is 40.5cm sq
Paper 2 - Q15 and the ans is $360
Paper 2 - Q17 and the ans is 120

http://postimage.org/image/jk1hymuc/

http://postimage.org/image/s3ym9sis/

http://postimage.org/image/240e8e9fo/

http://postimage.org/image/jk4t1btw/

http://postimage.org/image/jk6gkobo/

http://postimage.org/image/2aopcqyys/
[/img][/list]

[Vanilla Cake]

capricorn28:

Hi All,

Actual workings from DD2.


VC's mum

capricorn28:

Paper 2 - Q6 and the ans is 16 degrees

http://postimage.org/image/s3ym9sis/
Angle TUV =180⁰-60⁰=120⁰
Angle XWT=180⁰-170⁰=10⁰
360⁰-60⁰=300⁰
Angle XUT =360⁰-300⁰-34⁰-10⁰=16⁰

Angle XUT = 16⁰.

capricorn28:

Paper 2 - Q8 and the ans is 72%

http://postimage.org/image/240e8e9fo/
Before
L: 4u
F: 6u

After
L: 3.2u
F: 4u

(3.2u+4u)/10ux100% = 72%

72% of the stamps was left.

capricorn28:

Paper 2- Q13 and the ans is 80cm

http://postimage.org/image/jk1hymuc/
5u=8000 cm²
4u=6400 cm²
Square root of 6400 cm² = 80 cm

Length of the square = 80 cm.

capricorn28:

Paper 2 - Q14 and the ans is 40.5cm sq

http://postimage.org/image/jk6gkobo/
24÷8x5=15 cm
24-15 = 9 cm
40-9 = 31 cm
½x40x15 = 300 cm²
½x31x9 = 139.5 cm²
½x24x40 = 480 cm²
480-139.5-300=40.5 cm²

Shaded area = 40.5 cm²

capricorn28:

Paper 2 - Q15 and the ans is $360

http://postimage.org/image/2aopcqyys/
Before
J: 6u
K: 5u

After
J: 3.6u
K: 7.4u

In the end
J: 7.3u
K: 3.7u

7.3u-3.7u=3.6u
3.6u=$216
6u = $360

At first, Jude had $360.

capricorn28:

Paper 2 - Q17 and the ans is 120

http://postimage.org/image/jk4t1btw/
Hall (2n)
B : G
3u/4 : u/4
3 : 1
15 : 5

Canteen (1n)
B : G
2p/5 : 3p/5
2 : 3
4 : 6

1u=6
20u=120

Number of pupils in the hall = 120.

[Vanilla Cake]

wkong:

The figure is not drawn to scale. It shows a rectangle divided into 6 parts. Each part has a different area.

a) Find the total area of P and Q.
b) Find the perimeter of the figure.

http://www.postimage.org/

Use guess and check,
Area of P = 8 cmx 6 cm = 48 cm²
Area of Q = 5 cm x 4 cm = 20 cm²
(a) Total area of P and Q = (48+20) cm² = 68 cm²

Length of rectangle = (5+6+4) cm = 15 cm
Breadth of rectangle = (8+5) cm = 13 cm
(15x2)+(13x2) = 30+26 = 56 cm
(b) Perimeter of the figure = 56 cm