I know what I have to do, but I cannot identify the information I need to solve the question. Need help to identify the necessary information.

Q. The attached figure is made up of two pairs of identical squares of different sizes. DCG is a straight line. The sum of the area of 1 large square and 1 small square is 52 cm2.

(a) What is the area of the shaded portion?

(b) What is the ratio of the area of triangle AHC to the area of triangle ACG?

Darryl See wrote:
I know what I have to do, but I cannot identify the information I need to solve the question. Need help to identify the necessary information.

Q. The attached figure is made up of two pairs of identical squares of different sizes. DCG is a straight line. The sum of the area of 1 large square and 1 small square is 52 cm2.

(a) What is the area of the shaded portion?

(b) What is the ratio of the area of triangle AHC to the area of triangle ACG?
Hi Darryl See,
Using guess and check to get side of the large square as 6 cm and side of small square as 4 cm. Rest of the steps should be OK for you.Where is this question from?
Let's hear what Chris Rogers has to say.

Hi, Perseverance

Darryl is at school at the moment. I believe it's from his CA2 maths question. He posted it last night and asked me to lookout for answer from Onsponge. Looking at it now, and like you said, is to solve it by trial and error to determine the sides of the two different squares or knowing the ratio of the area of the different squares whose sum will added to the given value.

Is it usual to omit informing the student to use method of estimation to help solve the question?

Thank you

Yes, I was just looking at this question with in a live workshop with teachers I would approach it in a similar style by making a list of possible areas for the big and small square.
Total - Big = Small
52 - 1 = 53 (no)
52 - 4 = 48 (no)
52 - 9 = 43 (no)
52 - 16 = 36 (yes)

The only thing is we need to assume the solution uses whole numbers only.

Once we know that the area of the big square is 36cm2 and the small is 16cm2 we can arrive at the answer quite easily.
Area of one shaded triangle --> 1/2 x b x h --> 1/2x4x6 --> 12cm2
Area is of shaded figure is 24cm2

Yes this would be considered a 'normal' question. We learn "Guess & Check" and also "making a list" as approaches to problem solving.

You will find a number of similar questions in the P5 book in the Area & Perimeter Topic.

Darryl See wrote:
Hi, Perseverance

Darryl is at school at the moment. I believe it's from his CA2 maths question. He posted it last night and asked me to lookout for answer from Onsponge. Looking at it now, and like you said, is to solve it by trial and error to determine the sides of the two different squares or knowing the ratio of the area of the different squares whose sum will added to the given value.

Is it usual to omit informing the student to use method of estimation to help solve the question?

Thank you
The best person to answer your question will be Darryl's Maths teacher. I believe that guess and check is accepted as one of the approved problem solving strategies in PSLE Maths syllabus.When you can't think of other strategies and may have to resort to forming algebraic equations, why don't use guess and check which may be less efficient as compared to other methods.The ultimate goal is to secure full marks by providing the right answer and right method to the question under stressful exam conditions. So with good, logical and intelligent guesses, it will help you to secure these marks if you are in a desperate scenario.

For this question, you have to apply some educated number senses.If you don't get it right at your first attempt, try to tabulate your solution by forming a systematic list.Of course,there should be other methods to solve this question. I use guess and check solution so that forming algebraic equations can be avoided.

Let's wait for Chris Roger's comments.

Yes this is correct. For the PSLE there is no boundary placed on which methods you must or must not apply. The student may choose any method to solve the question and the markers will look at the answers and logic you have applied. So whether you use Models, Algebra, +hinkingMath strategies, some funny funny solution from nowhereland or making a list it doesn't really matter as long as it is logical. Of course if you get the wrong answer and your logic is "because I had a gut feeling" this will not result is full marks

In school, the teachers may request you leverage a particular strategy because they want you to understand and practice that particular approach but not because it is 'The One' accepted on the PSLE.

Gentlemen, (Roger n Perseverance)

Thank you for the valuable comments. And in particular,".....some funny funny solution from nowhereland .......and get the wrong answer and your logic is "because I had a gut feeling" this will not result is full marks. This is very good advice against using outlandish approach to solve mathematics even the answer(s) happens to be correct.

I will let Darryl know when he comes back from school.

As I have not seen the marked paper with correction, I am unable to comment on whether his teacher allows "Guess n Check" or only set strategy which I would love to see. But my guess is GnC could be the approach shown to the class.

My answers to the question were (a) 24 sq cm
(b) 3:1

Darryl See wrote:
I will let Darryl know when he comes back from school.

As I have not seen the marked paper with correction, I am unable to comment on whether his teacher allows "Guess n Check" or only set strategy which I would love to see. But my guess is GnC could be the approach shown to the class.

My answers to the question were (a) 24 sq cm
(b) 3:1
Refer to Observer's solution and pls share the solution given by Darryl See's school teacher for your P5 - Area of triangle problem.

Solution is the same ???

Making a list (and checking it twice).

Also noticed the date - it was posted yesterday. Really coincidental and lucky for us.