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# 2017 S1-07 MATHEMATICS

## Thursday, October 19, 2017

## Saturday, October 7, 2017

### Revision: SST 2016 Maths S1 Paper 2 Q4b

There are 2 ways to find

It uses the special products (or algebraic identities) to solve.

Note that we did not need to find

In this method, we attempt to solve 2 simple simultaneous equations to find out the values of

With this, we find

Some of you actually use "Guess and Check" method, where you try to list down possible pairs of integers that can be add together to give 7, followed by check using the other equation.

Do NOT use this method as it opens up many possibilities which would not worth the time to check one by one.

*xy*:

**Method 1:**(as shown in the suggested solution document, in GoogleSite)It uses the special products (or algebraic identities) to solve.

Note that we did not need to find

*x*or*y*value in this method.

Method 2:Method 2:

In this method, we attempt to solve 2 simple simultaneous equations to find out the values of

*x*and*y*.With this, we find

*xy*.Some of you actually use "Guess and Check" method, where you try to list down possible pairs of integers that can be add together to give 7, followed by check using the other equation.

Do NOT use this method as it opens up many possibilities which would not worth the time to check one by one.

### Revision: SST 2016 Maths S1 Paper 2 Q6

One strategy to solve this problem is to write down and organise the information available.

From there, try to pull the information together to form an equation to solve for the unknowns.

From there, try to pull the information together to form an equation to solve for the unknowns.

### Revision: SST 2016 Maths S1 Paper 2 Q7

Given the speed of the following:

Strategy: Put all information in a diagram and draw 'relationships' (with reference to the speed-time-distance formula) to form equations

Since we do not know the distance for the race, let it be

Since we are not given the time taken by Adam to complete the race, let the time taken be

The 2nd diagram shows the position of

Hence, what's common for all three boys is the duration,

Using the formula, Distance = Speed x Time

With this, we know that distance covered by Charlie (at t min) = 800

Substitute

Time taken,

= Distance covered/ Time taken

= 550

=

Note: There are other 'shortcuts' to solve the problem. However, the above will give you an idea how to solve the unknown(s) systematically using the known relationships for speed-time-distance.

- Adam 160 m/min
- Bernard 120 m/min

Strategy: Put all information in a diagram and draw 'relationships' (with reference to the speed-time-distance formula) to form equations

Since we do not know the distance for the race, let it be

*d*metres.Since we are not given the time taken by Adam to complete the race, let the time taken be

*t*minutes.The 2nd diagram shows the position of

**Adam, Bernard and Charlie at***t*minutes.Hence, what's common for all three boys is the duration,

*t*minutes.Using the formula, Distance = Speed x Time

With this, we know that distance covered by Charlie (at t min) = 800

*m*- 250*m*= 550*m*Substitute

*d*= 550 into first equation (i.e. time taken by Adam), we haveTime taken,

*t*= 800 ÷ 150 = 5 minutes*Hence, Charlie's speed*

= Distance covered/ Time taken

= 550

*m*÷ 5*min*=

**110**(Ans)*m/min*Note: There are other 'shortcuts' to solve the problem. However, the above will give you an idea how to solve the unknown(s) systematically using the known relationships for speed-time-distance.

### Revision: SST 2016 Maths S1 Paper 2 Q8

Watch the video clip (no sound) to understand the diagram

(i) Since the length of the paper is 30 cm, from the diagram, we note that

Height of letter in terms of

(ii) Given the ratio Height : Width = 8 : 5

Since we can express the height of the letter in terms of

Refer to the line (in orange), width = 3 +

Now, with these information, we use the ratio to form the equation and use it to find

(iii) To find the perimeter of the letter, we need to find the

(i) Since the length of the paper is 30 cm, from the diagram, we note that

Height of letter in terms of

*x =*30 -*x*-*x*cm, which is same as**30 - 2***x*cm(ii) Given the ratio Height : Width = 8 : 5

Since we can express the height of the letter in terms of

*x*, we shall try to express the width of the letter in terms of*x*, too.Refer to the line (in orange), width = 3 +

*x*cmNow, with these information, we use the ratio to form the equation and use it to find

*x*:(iii) To find the perimeter of the letter, we need to find the

*y*(marked out in the diagram)## Monday, October 2, 2017

### 20171002: Revision - Algebra

Mentioned in class, there's more than one way to do (i).

I've presented 3 ways below how to show LHS of equation = RHS of equation.

We also spoke about NOT using any numbers to do the "shown" question. Remember that "hence" means make use of what is given in (i) to do (ii)

Practice for similar type of Question: CGS 2015 S2 Mid-Year Section A Q7

I've presented 3 ways below how to show LHS of equation = RHS of equation.

We also spoke about NOT using any numbers to do the "shown" question. Remember that "hence" means make use of what is given in (i) to do (ii)

Practice for similar type of Question: CGS 2015 S2 Mid-Year Section A Q7

## Saturday, September 30, 2017

### 6 AM Quiz: It's Algebra!

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