Tutor MathsGuru: Ask me for your burning Maths questions!

[mathsguru]

MMM:

I've some questions for P3 and appreciate your help on how to approach the question. Taken this from P3 CH SA1 paper. I want to understand how to teach my P3 to approach such questions in the future as they don't give much information and subjected to interpretation.


43) Evelyn has 150 sweets more than Joyce. If Evelyn gives Joyce 38 sweets, how many more sweets will Evelyn have than Joyce?

THanks.

Hi MMM,

Here's my solution.

It's best to draw out a diagram to visualise it more quickly and easily, because the way the question is phrased can be very misleading at first glance. That's what I advise my P3 students as well.

Cheers,
MathsGuru

http://www.postimage.org/image.php?v=TswuvIi

[mathsguru]

:thankyou: for all your well wishes! *touched*


Keep the questions coming... :D,
MathsGuru

[lemofish]

lovekidsverymuch:

mathsguru:

http://www.postimage.org/image.php?v=TswuvIi

mathsguru the way of ur teaching very nice :celebrate: and makes the sum look very simple

I have a question:

40 children in Class A are having a muffin party. 26 of them eat a vanilla muffin each and 32 of them eat a chocolate muffin each. Everyone in the class eats at least 1 muffin. How many children eat both a vanilla muffin and a chocolate muffin?

[Guan Hui]

26+32=58(no of muffins ate)

58-40=18(If each child ate only 1 muffin there will be extra 18 muffins that was eaten)
Ans: 18 (so 18 of the children ate both vanilla and chocolate)

[Vanilla Cake]

Hi Mathsguru,

Pls help my P5 younger sister to solve this 4-mark question from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-ACS.pdf using models. Thank you.

The volume of water in bottle P was 3/5 of that in bottle Q. After 60 ml of water was added to bottle P and 20 ml was poured away from bottle Q, the amount of water in bottle P was 3/4 that in bottle Q. What was the amount in each bottle at first?

Other than models, what are your recommended method/s to tackle such problem sum?

[lemofish]

Got it! Thank you!

[Guan Hui]

Hi vanilla cake! ,

other ways.. for me the most convenient is of course algebra.

Algebra
P amount = x
Q amount = y
5x=3y-----1
4(x+60)=3(y-20)
4x+240=3y-60
4x+300=3y------2
5x=4x+300
x=300ml
y=500ml

Ratio(sort of)
P :Q
3units :5units
+60 -20
3 units +60= 3nUnits(nunits= new units)
1 nunit= 1unit+20
3 :4 (ratio is in nunit)
3u +60:4u+80

5 u-20=4u+80
1u=100
initially P have 3 u.. so 300ml.
Q have 5 u... so 500ml.


Hope you understand 1 of them=/

[speedmaths.012624com]

Vanilla Cake:

Hi Mathsguru,

Pls help my P5 younger sister to solve this 4-mark question from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-ACS.pdf using models. Thank you.

The volume of water in bottle P was 3/5 of that in bottle Q. After 60 ml of water was added to bottle P and 20 ml was poured away from bottle Q, the amount of water in bottle P was 3/4 that in bottle Q. What was the amount in each bottle at first?

Other than models, what are your recommended method/s to tackle such problem sum?

Hi Vanilla Cake,

The volume of water in bottle P was 3/5 of that in bottle Q.
After 60 ml of water was added to bottle P and 20 ml was poured away from bottle Q, the amount of water in bottle P was 3/4 that in bottle Q.
What was the amount in each bottle at first?

Let’s CHANGE the question (but still using the SAME numbers) to:

In a shop, the ratio of the number of apples to the number of oranges was 3:5, at first.
The shopkeeper bought 60 more apples, and sold 20 oranges.
As a result, the ratio of the number of apples to the number of oranges became 3:4.
How many apples and how many oranges, were there in the shop at first?

This is a typical Double-Ratio Question, quite common in the PSLE.

Using the Bags and Boxes Method (which can solve ALL such Double-Ratio Questions):
(Once you are familiar with the method, you can cut down some of the steps below)


At first, the apples / oranges were kept in Bags.
Each Bag contains the same number of apples / oranges.
There were 3 Bags of apples, and 5 Bags of oranges, at first.

After 60 apples were added, and 20 oranges were removed,
the apples / oranges were then kept in Boxes.
Each Box contains the same number of apples / oranges.
There were 3 Boxes of apples, and 4 Boxes of oranges.

Apples:
3 bags + 60 apples = 3 Boxes
(x 4)
12 bags + 240 apples = 12 Boxes

Oranges:
5 bags – 20 oranges = 4 Boxes
(x 3)
15 bags – 60 oranges = 12 Boxes

12 Boxes = 12 bags + 240 apples = 15 bags – 60 oranges
12 bags + 240 apples = 15 bags – 60 oranges
0 bags + 240 apples = 3 bags – 60 oranges
240 apples = 3 bags – 60 oranges
300 apples / oranges = 3 bags
1 Bag = 100 apples / oranges
There were 3 Bags of apples, and 5 Bags of oranges, at first.

There were 300 apples, and 500 oranges, at first. (ANSWER)

[Dharma]

Vanilla Cake:

Hi Mathsguru,

Pls help my P5 younger sister to solve this 4-mark question from http://www.orlesson.org/orp/09Ma/2009-Math-SA1-ACS.pdf using models. Thank you.

The volume of water in bottle P was 3/5 of that in bottle Q. After 60 ml of water was added to bottle P and 20 ml was poured away from bottle Q, the amount of water in bottle P was 3/4 that in bottle Q. What was the amount in each bottle at first?

Other than models, what are your recommended method/s to tackle such problem sum?

Hi Vanilla Cake,

Your sister may wish to look at this while waiting for Mathsguru’s solution.


http://www.postimage.org/image.php?v=gxEDrbJ

[OK Lor]

Hi Mathsguru,


The product of two numbers, A and B, is 108. The difference betweeen A and B is a common factor of A and B. Find the values of A and B.

Thanks.