Q&A - P3 Math

[MathIzzzFun]

fohope:

Hi,

Pls help to solve the problem sum. Thank in advance.

A group of classmates plan to buy a present for their teacher. If each of them pay sgd2.00, they will be short of sgd3.00 for the present.
If each of them pay sgd3.00,they will have an extra of sgd3.00. If there are fewer than 10 classmates, how much does the present cost ?

Hi

http://i45.tinypic.com/vimhyd.png\">

and using \"make a list\" heuristics ...

http://i48.tinypic.com/fyzloz.png\">

cheers.

[fohope]

tianzhu:

smartmummy:

[quote=\"fohope\"]Hi,

Pls help to solve the problem sum. Thank in advance.

A group of classmates plan to buy a present for their teacher. If each of them pay sgd2.00, they will be short of sgd3.00 for the present.
If each of them pay sgd3.00,they will have an extra of sgd3.00. If there are fewer than 10 classmates, how much does the present cost ?

Time table 2: 2 4 6 8 10 12 14 16 18
+3: 5 7 9 11 13 15 17 19 21
Time table 3:3 6 9 12 15 18 21 24 27
-3 : 0 3 6 9 12 15
Price is sgd 9

Hi

Making a table or Listing is a suitable method for this question as the numbers are small.

Do take note that the number of classmates remains the same in both tables.

The number of classmates is 6 and the price of present is 15.

Alternate ways are MD or using Gap and Difference.

3+3 ------ 6

Difference ------- 3-2 ------- 1

Number of classmates -------- 6/1

Present’s cost --------- (6*2) + 3 ------ 15

Best wishes[/quote]Thanks Tianzhu,SmartMummy and MathIzzzfun for your reply.

Hi Tianzhu,
Could you show me the table method?

[tianzhu]

fohope:

Hi Tianzhu,
Could you show me the table method?

Hi

Making a table is the same as Systematic Listing. It is presented in a tabulated list.

I am sorry.I am unable to do it today.

There are a few ways to tackle this question.

Please give me some time; I’ll prepare the slide showing the various ways and PM to you.

Best wishes

[peapot]

I found this similar q in Superstar online. Thought of sharing with everyone how they solve this q.


Firstly, whatever is short or extra must be distributed back equally to every kid. $3+$3 = $6. This $6 is distributed to all the kids. This means that 1 kid gets $1 each therefore there are 6 kids.

So to find the cost of the present, just take 6x2 = 12 and then 12+5=$15 for the present.

[allcc6]

MathIzzzFun:

Q2. Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be twice as old as his son?

The age difference will remain the same.

Age difference = 42 - 8 = 34

When Mr Tan is twice as old as his son, and since the age difference is 34, Mr Tan will be 2 x 34 = 68
68 - 42 = 26 --> Mr Tan will be twice his son's age in 26 years' time.

cheers.

Can anyone advise the steps if question is changed to :

Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be three times as old as his son?

[mrswongtuition]

allcc6:

MathIzzzFun:

Q2. Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be twice as old as his son?

The age difference will remain the same.

Age difference = 42 - 8 = 34

When Mr Tan is twice as old as his son, and since the age difference is 34, Mr Tan will be 2 x 34 = 68
68 - 42 = 26 --> Mr Tan will be twice his son's age in 26 years' time.

cheers.

Can anyone advise the steps if question is changed to :

Mr Tan is 42 years old and his son is 8 years old now. In how many years time will Mr Tan be three times as old as his son?

KEY CONCEPT: The age difference does not change.

Their age difference is 42 - 8 = 34 years.

Mr Tan [---][---][---]
Son `` [---]<--34-->

2 units --> 34
1 unit --> 34/2 = 17

17 - 8 = 9
Ans: In 9 year's time

[tracywham]

Hi, can i have some guidance using "models" to solve this question please. Thank you.


Clarence had 4 times as much as John. After spending $230 on clothes, Clarence still has $160 more than John. How much money did Clarence have at first?

The answer is $520.

[BigDevil]

http://i46.tinypic.com/2n6rert.jpg\">

[tracywham]

Oic.... i understand now... thanks for your illustration too...sometimes i just get confused with the before and after concept....

[Cher2101]

Hi can you please help me on these 2 questions.


1). Bao Ming wants to buy 6 shirts but he is short of $7. If he buys 5 shirts, he will have $11 left. How much money does Bao Ming have?

2). Ben had twice as many books as Eve. If Ben gave Eve 20 books, Ben will have 10 more books than Eve. How many books do they have altogether?