Q&A - P3 Math

[teh_oh]

Champion:

teh_oh:

Hi Tianzhu,


My child is in P3. His math has been his strongest subject so far as his school has yet to expose him to such challenging questions. Meanwhile, we are just maintaining once a week practices using exam papers to ensure that his foundation is strong and that he is on par with other school standards. This thread is our main source of challenging questions (with clear worked examples too! Thank you! :)) for him to practice. He challenges me to solve them as well and gets the kick of beating me to arriving at the solution. :oops:

Hi teh_oh,
Your son is very disciplined :congrats: . My girl who is also in P3 this year is very reluctant and resistant whenever she faced challenging problem sums in the assessment books. We were working on Andrew Er's book when she gave the remarks,\" This assessment book very difficult; can give it a pass?\" :lol: Guess, I will log into this thread more often to learn more.

Hi Champion,
Thanks for the compliments.
My boy does not have any other Math assessment books as he finds that doing pages for one full topic to be very dry/tedious. He prefers doing Math exam papers which offers a 'variety' of questions from different topics. We only do a paper a week as other precious time are spent on other subjects.
Tianzhu's colourful worked solutions and the novelty of 'doing sums off the computer' which seems appealing to my child, is now my free source of 'challenging sums'.

[plum-cake]

concerned1970:

Tysm Tian_zhu! It always gives me a BIG headache when comes to Math. U're a great and wonderful dad who's willing to spend time to do the revision with yr son. Not all men like u! It's not easy.

I agree. :goodpost:

[Champion]

Hi Tianzhu & all parents,

Need your help with the following questions that DD1 came home with worksheet from school.

(1) The sum of two numbers is 7500. The greater number is twice that of the smaller number. What are the 2 numbers?

(2) Kenneth has 9 coins that add up to $2.70. Some of them are 50-cent coins and the rest are 20-cent coins. How many 50-cent coins does he have?

(3) John and Samy shared 72 sweets. John received twice as many sweets as Samy. How many sweets did John receive?

Can advise me for the above types of questions, it shall be under addition/subtraction/multiplication/division? And how to show them using models?

Sorry to trouble you all but I am at a loss when coming to Maths :imsorry:

[tianzhu]

Champion:

Hi Tianzhu & all parents,

Need your help with the following questions that DD1 came home with worksheet from school.

(1) The sum of two numbers is 7500. The greater number is twice that of the smaller number. What are the 2 numbers?

(2) Kenneth has 9 coins that add up to $2.70. Some of them are 50-cent coins and the rest are 20-cent coins. How many 50-cent coins does he have?

(3) John and Samy shared 72 sweets. John received twice as many sweets as Samy. How many sweets did John receive?

Hi Champion
I take them as P3 questions.

Q1 and Q3 are pretty similar.
You may use MD to solve them.

Big number ------ 2 units (2 rectangular blocks)
Small number -----1 unit (1 rectangular block)

3 units ------7500
1 unit ------ 2500

The two numbers are 5000 and 2500.

John ------ 2 units
Samy -----1 unit

3 units ------ 72
1 unit ------ 24

John ------ 2 units ------- 48

For Q2, a P3 student may make calculated guesses using a strategy called GC. The numbers are small and it’s not too tedious to arrive at the solution.

Or, he/she may use a heuristics known as “Draw a diagram”

In this solution, I’ll share how to solve by “Make a Supposition”. This strategy is more efficient and is used commonly in upper primary level.

Assume all were 20 cents coins.

9*20 ------ 180
270 – 180 ------90

Difference between 50 cents coin and 20 cent coin -------- 30

90/30 -------3

Hence 3 50 cents coins

Best wishes

[Champion]

tianzhu:

Champion:

Hi Tianzhu & all parents,

Need your help with the following questions that DD1 came home with worksheet from school.

(1) The sum of two numbers is 7500. The greater number is twice that of the smaller number. What are the 2 numbers?

(2) Kenneth has 9 coins that add up to $2.70. Some of them are 50-cent coins and the rest are 20-cent coins. How many 50-cent coins does he have?

(3) John and Samy shared 72 sweets. John received twice as many sweets as Samy. How many sweets did John receive?

Hi Champion
I take them as P3 questions.

Q1 and Q3 are pretty similar.
You may use MD to solve them.

Big number ------ 2 units (2 rectangular blocks)
Small number -----1 unit (1 rectangular block)

3 units ------7500
1 unit ------ 2500

The two numbers are 5000 and 2500.

John ------ 2 units
Samy -----1 unit

3 units ------ 72
1 unit ------ 24

John ------ 2 units ------- 48

For Q2, a P3 student may make calculated guesses using a strategy called GC. The numbers are small and it’s not too tedious to arrive at the solution.

Or, he/she may use a heuristics known as “Draw a diagram”

In this solution, I’ll share how to solve by “Make a Supposition”. This strategy is more efficient and is used commonly in upper primary level.

Assume all were 20 cents coins.

9*20 ------ 180
270 – 180 ------90

Difference between 50 cents coin and 20 cent coin -------- 30

90/30 -------3

Hence 3 50 cents coins

Best wishes

Hi Tianzhu,
Thanks so much for your detailed explanation; appreciates :thankyou:

Yes, the above questions are meant for P3 but was rather stunned when I looked at the worksheet when DD brought back today. Reason being that she has not being taught Division and the relief teacher solved Q1 using division: 7500/3 = 2500. Then 2500x2=5000. Big number 5000 and small number 2500.

So I decided to post the questions to seek help from you and other parents. After seeing your analysis, I grasp more concepts lioa

[Nebbermind]

are the p3 taught division like the way we used to do…working with the ‘biggest’ number, get the remainder, repeat until the smallest number?


I don’t remember my boy having to go thru that…and eventually they all use calculators.

[tianzhu]

Champion:

Hi Tianzhu,
Thanks so much for your detailed explanation; appreciates :thankyou:

Hi Champion

You're welcome.

Best wishes

[deep]

Before a game, Benson had 3/5 as many marbles as Sharul. During the game, Sharul lost 63 marbles to Benson, after which Benson had twice as many marbles as Sharul. How many marbles did Benson have at first?

[tianzhu]

deep:

Before a game, Benson had 3/5 as many marbles as Sharul. During the game, Sharul lost 63 marbles to Benson, after which Benson had twice as many marbles as Sharul. How many marbles did Benson have at first?

Hi

You may use the Units Method.

At first
Benson ----- 3 units ------- 9 units
Sharul ------ 5 units ------- 15 units
Total ------- 8 units -------- 24 units

In the end.
Benson ----- 2 units -------- 16 units
Sharul ----- 1 unit ------- 8 units
Total ----- 3 units ------- 24 units

The total number of marbles before and after the transfer remains the same. Make the total number of units before and after the same.A common multiple of 3 and 8 is 24.

Difference in units ------ 7 units
7 units ------63
1 unit ------- 9

Benson ------ 9 units ------- 81 marbles

Best wishes

[deep]

Why is it become 9 and 15? cant understand that…