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# What Makes A Good Resource - Calculating with Standard Forms

This page has been archived. The content was correct at the time of original publication, but is no longer updated.
Created on 08 September 2009 by ncetm_administrator
Updated on 03 September 2010 by ncetm_administrator

# Calculating with Standard Forms

Resource description:
The resource is a table with three columns: one has a calculation, one has the answer in standard form and the final one has the answer in ‘normal’ numbers.

I had done some teaching of indices and converting between standard form and normal prior to this lesson.

Teacher comment:
Each year when I teach standard form, it is very much focussed on ‘this is how you change to standard form, then this is how you change it back and this is how you use it in calculation’. This year I thought that the students could do with a more integrated approach and combine all three activities.

What I did:
The table was handed out to pairs. They had to cut up the table and then match the various cells together. There are two blank cells that had to be filled in. Once complete, the pair had to take half the matches and glue them in their books with an explanation as to why they matched. They had to have one blank each.

Reflection:
The students found this a challenging exercise. Most of them matched the numbers and standard form together very quickly and then started working on the calculations. A few students noticed that, for example, (6x10-3)÷(2x10-4) had to be 30 because 6 ÷ 2 is 3 and no other answer started with a 3. This led into discussions about 10-3÷10-4  and how to work this out. This then provided a springboard for matching other triplets.

During these conversations, I was walking around the room, listening and prompting. The students were comfortable with the idea of using the rules of indices to help do these sorts of calculations, but many of them were getting bogged down with actually calculating -3 – (-4). Some students I helped by drawing a number line and showing how it worked, but in future I would do a recap of calculating negative number prior to this lesson because I was unhappy with how many students thought the above calculation had the answer 7. (There are other suggestions on here how to combat this: have a look at “Teaching Negativity” by Chris Haynes, “Subtracting negative numbers” by Matt Cooper or “Number Tablets” by Tom Rainbow, all of whom have excellent ideas for tackling this).

The crucial part of this lesson for me was that the students did not immediately put their hands up and cry “help!” They could all start the task and make good progress before hitting a sticking point. This enabled me to target my intervention so that all students could get something out of the task

Through group work all students managed to match most, if not all, the cards by the end of the lesson. I was more interested in the explanation as to why they matched to see if the students understood how standard form really worked and so if I was to run this again, I would stop the groups after they had matched one pair and write a full explanation of their thinking. This could be in their books or on a poster, but the detail of their thinking is crucial.

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