Q&A - P3 Math

[tianzhu]

Hi concerned1970


The solution for your first question.

As for Q2, Q3 and Q5, you may do them using GC or Systemmatic Listing. For Q2 and Q5, you may also consider \"Make a Supposition\" (Assumption Method).Try them out first.

Best wishes.

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[concerned1970]

Gd afternoon, it is P3 ques. Tysm for yr generous help. I know the ans to all ques but my son still doesn't get it when I tried to explain it to him. That's why I need yr help with yr models. So sry to trouble u.

[tianzhu]

concerned1970:

Gd afternoon, it is P3 ques. Tysm for yr generous help. I know the ans to all ques but my son still doesn't get it when I tried to explain it to him. That's why I need yr help with yr models. So sry to trouble u.

Hi concerned1970

You're welcome.

It’s important to know that MD is one of many heuristics in the primary maths syllabus. Besides MD, it’s good to consider other problem solving strategies as it offers students greater versatility in problem solving.

A student with a wider range of strategies is better able to adapt to challenges when he/she faces unfamiliar questions in examinations. Just like football, a team is able to change shape when dealing with different opponents.

A bill of $72 was paid with $10, $5 and $1 notes, if 13 notes were used for payments, how many notes of each kind were used?

For this question, it helps if a student is well versed in number bonds.

A little bit of planning helps to avoid unnecessary guesses.

The bill of 72 has a number bond of 60 and 12.
12 ------ 10+2 or 10+1+1 or 5+5+1+1, we are using 2 because we are dealing with multiples of $5 and $10.

So we need 2 $1 note, leaving a difference of $70 (72- 2 -----70)

You may start with GC or Listing

Set up a tabulated list with $10, $5 and $1 as headings.

Make calculated guesses to get a number of $10 and $5 notes (total number of 11 with a value of $70).

It shouldn’t be too tedious to arrive at 3 $10 notes and 8 $5 notes.

(3*10) ----- 30
(8*5) ----- 40
(2*1) ------ 2

Therefore we have 3 $10 notes, 8 $5 notes and 2 $1 notes.

Try out the other two questions, if you need any help, please let me know.

Best wishes

[concerned1970]

Hi Tianzhu, I got different ans for ques 3 (dollar notes). 3 $10, 8 $5 and 2 $1. Is there any other method to work out this pb sum besides guess and check method? I duno how to draw models for ques 2 and 5. Can you help me with the models drawings? Ty.

[teh_oh]

concerned1970:

5) Mr Li bought 100 fish for $100. He paid $3 for each big fish and $1 for 3 small fish. How many big fish and how many small fish did Mr Li buy?

Hi,
Is the answer
25 Big Fish and 75 Small Fish?

(while i still scratching my head, my child gave me this answer.......but he said he use trial and error. :oops:)

[tianzhu]

concerned1970:

Hi Tianzhu, I got different ans for ques 3 (dollar notes). 3 $10, 8 $5 and 2 $1. Is there any other method to work out this pb sum besides guess and check method? I duno how to draw models for ques 2 and 5. Can you help me with the models drawings? Ty.

Hi concerned1970

I am sorry.I misread it as $2 notes instead of $1 notes.

I'll revise the solution.

I am sorry for the inconvenience.

For Q3, GC or Listing is quite appropriate for P3 students.It takes a little of planning and logical thinking, and it's not too tedious to arrive at the solution.

For Q2 and Q5, GC or TE is also suitable at P3 level.Again the numbers are not too big, so it is not too tedious to make calculated guesses.

I don't think MD is appropriate for Q2 and Q5.
However, \"Make a Supposition\" is a more efficient method to solve such questions.It is usually used by pupils in upper primary.

I'll try to do them tomorrow.

Best wishes

[tianzhu]

teh_oh:

Is the answer
25 Big Fish and 75 Small Fish?
(while i still scratching my head, my child gave me this answer.......but he said he use trial and error. :oops:)

Hi

Your answers are correct.

Best wishes

[teh_oh]

tianzhu:

teh_oh:

Is the answer
25 Big Fish and 75 Small Fish?
(while i still scratching my head, my child gave me this answer.......but he said he use trial and error. :oops:)

Hi

Your answers are correct.

Best wishes

Hi Tianzhu,

Thanks! Anyone can post the workings? My child solved it using trial and error.

Looking forward....

[tianzhu]

teh_oh:

Hi Tianzhu,


Thanks! Anyone can post the workings? My child solved it using trial and error.

Looking forward....

Hi teh_oh and concerned1970

A quick one first using “Make a Supposition”. I’ll try to put up the solution in tabulated form using PowerPoint at a later time if there is a need.

Suppose there were 100 big fish.

We have 100B ----- $300 (100B ---- 100 big fish, and 100*3 ------$300)

Consider a group of 3 small fish @ $1

97B and 3S ------- $292 (97 big fish and 3 small fish ----- 292)

300 – 292 ------8

So, every increase of 1 group of 3 small fish will lead to a drop of $8.

300 – 100 -----200
200/8 ------25

We have 25 groups of 3 small fish, which is 75 small fish.

Hence we have 25B and 75S.

Best wishes

[teh_oh]

Thanks Tianzhu.


Can't believe this is the standard P3 questions nowadays.