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.