Maths Common Mistakes 3

Dear all,

Here is the continuation of the maths common mistakes.

Topic: FRACTIONS

Fractions stresses on the importance of identifying the correct NUMERATOR AND DENOMINATOR. The definition of fraction refers to parts out of a whole.

In the fraction



3 is the numerator while 4 is the denominator. DENOMINATOR refers to the total number of parts of a whole while NUMERATOR refers to the number of given parts.

Pupils need to be able to identify the correct numerator and denominator of a fraction.

In this equation of adding fractions,



The most common mistake to simply add up both the numerators and denominators to get a final answer of 3/8 (3 out of 8). THIS IS WRONG.

WE ADD UP THE NUMERATOR! but we DO NOT add up the denominator! THIS IS AN IMPORTANT RULE FOR fractions. Be it adding or subtraction, we do not add up the denominator.

The most important rule when we compare fractions or add and subtract fractions is to LOOK at the DENOMINATOR FIRST! Ask yourself

"Are the denominators the same? If they are not the same, how do I change them into the same denominator?"

- USE either the lowest common multiple method or
- you can multiply both their denominators together



Remember that if both the numerators and denominators are the same number, like 2/2 or 8/8, the fraction makes one whole.

Now, take a look at this question.

"Tom cut his cake into 9 slices. His mother are 2/3 of the cake. How many slices are left?"

COMMON MISTAKE: Pupil will leave the answer as a fraction. (1/3)

The correct answer should be 3 slices. remember, if you see the words slices or pieces, the answer should be a whole number and not a fraction.

SA2 begins....

Dear all,

Just a note. Scroll down to revisit the older posts by me. The Maths Common Mistakes are located in the older posts if you scroll down. :)

Good luck for your SA2 English paper 1 tomorrow.

Tomorrow, you will get back your mathematics files. We will try to finish up our corrections. I will be talking to some of you who still make the same mistakes for some topics. I want everyone to minimize their errors so that you can do the best you can. My aim for 3G8! 100% band 1s! We can do it together! So, we have only 15 marks to lose only! There is no room for error. We must cut down on common mistakes and careless mistakes.

You may find me naggy! But I will still repeat this! Do not assume! Read as you highlight key words. Take note of your units of measurement. It may sound simple but still, many of you will read the question wrongly. Take your time to check and read through after you have completed and have time left.

I promise to put up the remaining maths common mistakes by the weekend. :)

ALL THE BEST!

Sincerely,
Mr Nelson Ong

12th October 2011

Dear all,

Homework for today if you have not finished:

1. Speed maths fraction practice
2. Revision practice worksheet (questions pulled out from revision set B)

It is important to revise and look through Set A and Set B while doing your revision. Parents, do take note too. Look through the key questions (as I have gotten each student to highlight and indicate in your practice papers). These revision papers are a good source of practice for your SA2. I will be going through Set A tomorrow and will give back the Maths File this Friday for your revision!

I will put up more Maths Common Mistakes soon. Stay tuned.

Have a good day and do remember to return your parents' survey form by tomorrow!

Meanwhile, congratulations to 7 students in our class who got distinctions for their ICAS (New South Wales) Maths Competition 2011 with one honourable HIGH DISTINCTION.

HIGH DISTINCTION

1. Zachary Tan Jun Long

DISTINCTIONS

1. Irving Shua

2. Samuel Tan Yu Xuan

3. Ryan Ang Bing Hui

4. Varick Teo

5. Ryan Teo Zhang Rong

6. Ng Juin Yi

Well done once again! :) You have done the class proud.

Sincerely,
Mr Nelson Ong

Maths Common Mistakes 2

Topic: Time

1 hour = 60 minutes and NOT 100 minutes. This is one common mistake that some students do make.

E.g 3h 10min = _______min

For this above example, students who made the error will answer as 310 mins which is WRONG. As 1 h = 60mins, 3 hours = 3 x 60min = 180min. 180min + 10 min = 190min

So the final answer is 190min.

Another common error here is that WE DO NOT ADD A GIVEN TIME with a time duration, e.g

7.15am + 30 min = 7.45am (THIS IS A WRONG MATHEMATICAL STATEMENT!THIS IS VERY IMPORTANT!)

Many of the students still make this mistake, so please refrain from committing this error.

*Knowing these common mistakes and not making such mistakes will aid you greatly in minimizing the loss of precious marks for your SA2. These marks lost can sometimes determine if you score a band 1 or a band 2. So it is very important to make sure you spot the common mistakes and not make them!

If the question asks you what is 30 mins after 7.15am, the correct representation is to use a TIME LINE!



The above shows how a timeline is drawn. Take note that you need to indicate the units of measurement such as min, whether the time is AM, PM.

The next common mistake appears for such a question here:
Find 2 hours after 11am. Students will carelessly write the answer as 1am.

The answer should be 1PM! You need to take note of the 24 hour format.

6AM - 7AM - 8AM - 9AM - 10AM - 11AM - 12PM - 1PM - 2PM - 3PM - 4PM - 5PM - 6PM - 7PM - 8PM - 9PM - 10PM - 11PM - 12AM - 1AM - 2AM - 3AM - 4AM - 5AM - 6AM ..........

Please don't be too quick to answer the question. Stop! Look! Think! And fill in the correct units of measurement.

This website is also useful to learn about time.

http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks2/maths/time/index.htm

http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks2/maths/timetables/index.htm

We can only add duration of time together such as 10min + 10min = 20min. Never EVER add a time with a duration of time as shown above. Please Please Please take note and extra caution!

Another important question to take note of:

E.g The time on a clock shows 10:30pm. This time is 10 mins faster. Find the actual time. Some pupils will give the answer of 10:40pm just because they see the word 'faster'. That is not necessarily the case! Do take note. The actual time in real life is 10 mins slower than the clock.

Thus, it should read 10:20pm.

Maths Common Mistakes 1

Topic: Money

Pupils tend to convert $ to cents wrongly. REMEMBER that $1 = 100 cents and not 1000.

So $1 = 100 cents
and $10 = 10 x 100 = 1000 cents

Topic: Length, Mass and Volume

Before you start, you need to memorize by hard of the conversion of length, mass and volume.

1m = 100cm
1km = 1000m

1kg = 1000g

1 litre = 1000ml

You can use this simple test to test if you have gotten the correct units of measurement for each topic
http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks2/maths/measures/index.htm

Pupils tend to convert wrongly and thus, the whole question will be wrong. Keep practising on your conversion of units if you are unsure. Practise makes perfect.

One important skill that you need to have is to be able to read off a weighing scale. I find that about half the class still have difficulty reading off the scale.



This weighing scale reads up to 600g. To find out the value of one small marking, we will first count the number of markings from 0 to 100g, starting with the marking AFTER 0 right up to 100g.

This circled in red in the following picture.


From 0 to 100g, the value of all the markings are 100g. There are a total of 10 markings. Thus, one marking is 100g ÷ 10 = 10g. One marking stands for 10g.

The scale reads 470g.

The same skill also applies for reading a measuring cylinder!

Maths Common Mistakes

Dear parents and all,

I will be posting up a series of common mistakes that SHOULD BE AVOIDED. I will compile and go through the topics. :)

Sincerely,
Mr Nelson Ong

Countdown to SA2

Dear parents,

I have just given out an important form to each student to bring home today. On the form is the parents' survey that needs to be completed in either english or chinese. Do complete and get your child to return back by 13th October (Thursday) so that the school can collate the results.

Thank you so much for your help.

Sincerely,
Mr Nelson Ong.

Dear all,

I will be going through revision papers Set A and B on Wednesday. So if you have not passed up yet, please do so by tomorrow.

It is 4 days more to the start of SA2. It is really important to study hard and do your best for every subject.

Wednesday's supplementary lesson will be cancelled as I will be down for oral examinations duties after school.

Tomorrow, I will be going through important questions and common mistakes that you should not be making for mathematics.

Have a good rest and see everyone tomorrow.

PS: Please take good care of your health and stay healthy through this month. The weather has been bad. Do drink water and keep yourself warm.

Sincerely,
Mr Nelson Ong