Q&A - P5 Math

[blueymum]

Dear all


Apologies. Just wanted to see if there’s any possibility of using model to explain the question. Once again, really appreciate all your help.

A baker has some flour. He uses an equal amount of flour to bake cakes everyday. After 6 days, he has 3/5 of the flour left. After another 4 days,he has 15kg of flour left. How much flour did he have at first?

[tianzhu]

blueymum:

Dear all


Apologies. Just wanted to see if there's any possibility of using model to explain the question. Once again, really appreciate all your help.

A baker has some flour. He uses an equal amount of flour to bake cakes everyday. After 6 days, he has 3/5 of the flour left. After another 4 days,he has 15kg of flour left. How much flour did he have at first?

Hi

It’s possible to use MD.

Draw a bar and divide into 15 units. (3/5 ------ 9/15)

6 units ------ amount of flour used in 6 days

3/5 of 15 units ------- 9 units

1 unit ------ 1 day
4 units ------- 4 days

9-4 ------- 5

5 units ------- 15
1 unit ------- 3

15 units ------ 3*15 ------45

Best wishes

[concerned1970]

Gd morning all!

I need help in solving top sch ques;

1) Kanxi is 5 times as old as Jaycee this year. Jaycee is 9 years old now. In how many years’ time will Kanxi’s age be twice that of Jaycee?

2) What is the smallest possible number which will give a remainder of 3 when divided by either 12 or 15?

3) Find the value of 45+(42-12)/6x5
Which operation shall I work out first after brackets? Multiplication or division?

May I know how to copy and paste the text from the top sch paper online? I tried but didn’t work, is there any other method cos it’s quite troublesome to type everything out.

[mathfreak]

concerned1970:

Gd morning all!

I need help in solving top sch ques;

1) Kanxi is 5 times as old as Jaycee this year. Jaycee is 9 years old now. In how many years' time will Kanxi's age be twice that of Jaycee?

2) What is the smallest possible number which will give a remainder of 3 when divided by either 12 or 15?

3) Find the value of 45+(42-12)/6x5
Which operation shall I work out first after brackets? Multiplication or division?

May I know how to copy and paste the text from the top sch paper online? I tried but didn't work, is there any other method cos it's quite troublesome to type everything out.

Solutions:

1) Ratio of their current age:
Jaycee : Kanxi = 1 : 5.
Ratio of their future age:
Jaycee : Kanxi = 1 : 2.
The difference in age between two people will always remain the same no matter what. So we try to make the difference in units the same:
Current age:
J : K : Diff. = 1 : 5 : 4
Future age:
J : K : Diff. = 1 : 2 : 1 = 4 : 8 : 4
Since 1 unit is 9, and the difference is either 4-1 or 8-5 = 3 units, Kanxi's age will be twice that of Jaycee in 9x3 = 27 years.

2) The lowest common multiple of 12 and 15 is 60. We can find this by either listing, or the prime factorisation method (for more advanced learners).
Hence, the lowest such number is 60+3 = 63.

3) 45+(42-12)/6x5
= 45+30/6x5
= 45+5x5
= 70.
Note that 30/6x5 is not equal to 30/(6x5). There is a difference. Whenever multiplication and division or addition and subtraction occur next to each other, we do it from left to right. So, for example, 45-1+1 = 45, and not 45-(1+1) = 43.

[concerned1970]

Hi mathfreak, tysm for yr help. Btw, I dun get it why was that has to add 3 to 60 to get 63 for ques 2??


Someone pls kindly help me solve this pb sum.

For every bottle of perfume sold, Jessie gets $13. She also gets an extra $15 for every 9 bottles sold. How much money will she get if she sells 100 bottles of perfume?

[tianzhu]

concerned1970:

Hi mathfreak, tysm for yr help. Btw, I dun get it why was that has to add 3 to 60 to get 63 for ques 2??


Someone pls kindly help me solve this pb sum.

For every bottle of perfume sold, Jessie gets $13. She also gets an extra $15 for every 9 bottles sold. How much money will she get if she sells 100 bottles of perfume?

Hi

One way to do it is to use the Grouping Concept.

1 bottle of perfume ------- 13
9 bottle of perfume ------- 13*9 ------- 117

She also gets an extra $15 for every 9 bottles sold.

For every group of 9 bottles of perfume, she’ll get 132 (117+15)

100 ------99 + 1

There are 11 groups of 9 bottles of perfume.

(11*132) -------1452
1452+13 ------ 1465 (amount for selling 100 bottles of perfume)

Best wishes

[tianzhu]

concerned1970:

May I know how to copy and paste the text from the top sch paper online? I tried but didn't work, is there any other method cos it's quite troublesome to type everything out.

Hi

If you want to ask a question from past years papers (available online), you can list down the question number and provide a link to the test paper. It saves you the time for typing.

For example, Nan Hua CA1 Paper 2 P6 2011,Q7, please go to page 13 of this link.

http://www.orlesson.org/orp/11Ma/2011-P6-Math-CA1-NanHua.pdf

Best wishes

[concerned1970]

Tysm Tianzhu!


Btw, can u solve this ques for me? Cos my kids and I still dun get it. The method given by mathfreak was too profound for us to comprehend.

1) Kanxi is 5 times as old as Jaycee this year. Jaycee is 9 years old now. In how many years' time will Kanxi's age be twice that of Jaycee?

[mathfreak]

concerned1970:

Hi mathfreak, tysm for yr help. Btw, I dun get it why was that has to add 3 to 60 to get 63 for ques 2??


Someone pls kindly help me solve this pb sum.

For every bottle of perfume sold, Jessie gets $13. She also gets an extra $15 for every 9 bottles sold. How much money will she get if she sells 100 bottles of perfume?

If a number leaves a remainder of 3 when divided by n, it means that it is 3 more than a certain multiple of n. For example, 33 leaves a remainder of 3 when divided by 10, and it is 3 more than the third multiple of 10 (30). So we added 3 to the lowest common multiple of 12 and 15 to get the lowest number that leaves a remainder of 3 when divided by 12 and 15.

[tianzhu]

concerned1970:

Tysm Tianzhu!


Btw, can u solve this ques for me?

Hi

Kanxi is 5 times as old as Jaycee this year. Jaycee is 9 years old now.

Jaycee ------- 9
Kanxi ------- 45
Difference in age --------36

The age’s difference between two people always remains the same.

For Kanxi's age be twice that of Jaycee, Kanxi will be 72 years old and Jaycee will be 36 years old.

36 – 9 ------ 27

So the answer is in 27 years time.

Best wishes