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[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

[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.

[Vanilla Cake]

ck123:

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?

Hi ck123,
While waiting for KSP members to post model solutions, perhaps you may wish to refer to http://www.onsponge.com/forum/35-thinkingmathonsponge/3436-p5-math-unchanged-total.html.

[kancheongmum]

youngtay:

Hi, Please help


1. Lifen paid $180 for a pair of glasses. The amount she paid includes 7% GST.

a) How much GST did she pay? (Answer given $12.60)
b) What was the sale price of the pair of glasses? (Answer given $180)


2.During a sale, the price of a dining table was reduced from $699 to $350. It was given a further 20% discount on the new price after two weeks. How much was the total discount given? (Answer given $400.20)

Are the answers correct?

TIA

Hi youngtay
All the given answers are wrong
Q1) (a) $11.78 (b) $168.22

Q2) $419

I am sure you can work them out. Let me know if you need further help.

[Vanilla Cake]

wkong:

Roy had 6 times as many stamps as Colin. After their friend gave 4 stamps to Roy and 16 stamps to Colin, Roy had 4 times as many stamps as Colin. How many stamps did Roy have in the end?

Roy : Colin
6u : u
+4 : +16
4p : p

Roy : Colin
6u : 4u
+4 : +64
4p : 4p

6u+4=4u+64
2u=60
u=30

Roy (in the end)-> 6u+4 = 6(30)+4=184
Number of stamps that Roy had in the end = 184

[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.

[Almighty]

Vanilla Cake:

Almighty:

Hi VC,

Do u have the link for the answers to the following qts?
1) RGS Prelim 2010 (2 marks)
There are 3 containers X, Y,Z.
One contains blue amrbles, another white and the 3rd one a mixture of blue and white marbles and all are label wrongly.

Here's the http://www.onsponge.com/forum/35-thinkingmathonsponge/5534-p6-rgs-2010-math-p1-q23-30.html with excellent explanations by Zhou Shicai and Reynold Tan from OnSponge forum.

Thankyou very much VC.Wht a g8t timely help 4 both my qts!!!

[ck123]

Thanks vanilla cake

[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