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# Secondary Magazine - Issue 132: Eyes Down

Created on 13 April 2016 by ncetm_administrator
Updated on 27 April 2016 by ncetm_administrator

# Eyes Down

Have I assumed too much?

I’ve been stumped as to why so many students in my year 10 group failed to answer this question correctly:

I know to expect students to confuse rounding to a given number of significant figures with rounding using decimal places and until now they were always areas that I thought that I was pretty good at teaching – students were able to quickly recognise why they weren’t awarded accuracy marks in an assessment and rarely made the same mistake twice as I’d make a point of highlighting the misconception and it would result in a real “facepalm” moment for the student.

However, I only started teaching the vast majority of this group at the start of the academic year so they have different starting points and I think I made the mistake of over-estimating their ability with what I consider to be basic “maths”. I had assumed that they would be fluent in the two different rounding strategies and because of this I haven’t been regularly reinforcing the “rules” and “special cases” through rounding answers to varying degrees of accuracy when working on other areas of Maths as I would have done had I taught the topic from first principles.

Luckily I’m going to able to rectify this quickly as we move to focusing on “error intervals” I will be able to spend a few lessons looking at “where”, “when” and “why” the two different methods of rounding are used. It is important to remember that in some cases, the students will remember “rounding rules” from primary school which may need unravelling – it isn’t uncommon for students to think that it is always appropriate to round to the same number of decimal places (usually 2) if the level of accuracy used is always the same. In terms of significant figures I like to use number lines or scales in the first instance as I’ve found that it is easy to confuse students if all the rules are presented to them at the same time, especially given that there are special cases to consider.

Wish me luck!

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