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Fractions and Decimals - HELP!

Discussion in 'Primary' started by bestcoast, Mar 13, 2012.

  1. bestcoast

    bestcoast New commenter

    I'm an NQT teaching a Y4/5 class who are generally working at a 3B.
    They seem to have a grasp of fractions (of shapes, amounts and number) but I'm really struggling to get them to understand how these relate to decimals!
    Any ideas on how to teach this effectively?
  2. bestcoast

    bestcoast New commenter

    I'm an NQT teaching a Y4/5 class who are generally working at a 3B.
    They seem to have a grasp of fractions (of shapes, amounts and number) but I'm really struggling to get them to understand how these relate to decimals!
    Any ideas on how to teach this effectively?
  3. garem

    garem New commenter

  4. chocolateworshipper

    chocolateworshipper Occasional commenter

    Well done for getting them to grasp fractions! How about dividing up circles / squares / rectangles into 10 equal pieces - and colour in some of the pieces. Then draw columns with headings of tens, units, tenths, hundreths, and get the children to work out what should go in the tenths column. So for example, if 5 out of the 10 pieces are coloured red, then there are five tenths - so you put a 5 in the tenths column. I am hoping this makes sense! I would be very interested to see what others advise as I do not in any way claim to be an expert!
  5. Can they divide using the standard method? I call it the bus stop method, but I'm sure that's not a standard term! If so, get them to understand that 1/2 = 1 divided by 2. I get them to relate a fraction to a divide sign. The dot at the top and the bottom of a division symbol represents a number. If you divide 1 by 2, you get 0.5. If they are not confident using the standard method, get them to use calculators as an investigation. 1 divided by 2 will equal 0.5. Which other numbers will get the result of 0.5? Which 2 numbers will divide to get 0.25? What are the connections between all the numbers that get a result of 0.25?
  6. bestcoast

    bestcoast New commenter

    I've still got a few who are struggling to acknowledge that 1/4 is bigger than 1/8 (until I ask them if they'd rather share a cake with 3 other people or 7!)
    Thank you all for your ideas! I'll give them a go this week and let you know how it goes!
  7. Andrew Jeffrey

    Andrew Jeffrey New commenter

    Hi Amysan, another nice thing you could ask them to investigate is which fractions can be written as decimals and which can't. To do this at their level, give them a calculator (gasp!) and ask them to write 1/2 which they should type in as 1 divided by 2, and record the 0.5 that comes up.

    Try this with a few other fractions and compare. 1/3 gives a recurring answer.1/4 is 0.25 while 1/8 gives 0.125 - which is larger?! A bit of time on this should help them get to grips with the concept that numbers can be written in different ways. A useful phrase is that 'decimals are just special types of fractions, whose denominators are 10, 100, 1000 etc.
    Good luck!
  8. bestcoast

    bestcoast New commenter

    That sounds like a great idea. Sorry to sound a bit thick but what do you mean by fractions that can't be written as decimals? Would you include 1/3 in this category?
    I'm moving onto percentages next week, I think they will gain a much better understanding of this (i.e. understanding that 100% = 1 whole etc.) Has anyone else had difficulty teaching fractions/decimals?
  9. Surely this falls into the same category as telling children, when doing column subtraction, that you 'can't do' 3 - 7 etc.
    Be very careful putting these kinds of ideas into children's heads - simple phrases like these can cause large errors in understanding later on!
  10. Andrew Jeffrey

    Andrew Jeffrey New commenter

    Sorry if I was unclear! I am just as much against the 'can't take 7 from 3' as anyones else, or the 'adding a zero' come to that. Here's a better explanation (hopefully!)There are some fractions (specifically those with denominators of 3,6,7,9 or multiples thereof) which cannot be expressed exactly as decimals. When a calculator does so, it will show the first few digits of a recurring decimal, and this gives the opportunity for an interesting and useful discussion.

    Those fractions with denominators of 2,4,5,8 or their multiples can be expressed exactly as decimals. Thank you salofi - my fault for trying to get away with half an explanation!
  11. Some calculators have no problem displaying recurring decimals, at least if their period is not too long.

    Also, you don't mean multiples of 2,4,5,8. This would include 24 for example. You mean numbers of the form 2^a*5^b where a and b are integers >= 0.

    Sorry about that.
  12. Andrew Jeffrey

    Andrew Jeffrey New commenter

    Yes you're right - not enough caffeine in my system yet - thanks!
  13. Anonymous

    Anonymous New commenter

    I don't want to sound rude but fractions to decimals and percentages are quite tricky concepts if you have children at 3b in year 4/5. I tutor children in secondary school who struggle with such concepts.
    Personally I'd stick to simple fractions e.g. 1/4, 2/5 and maybe stick to simple percentages 25%, 50%
    Fractions to decimals is incredibly tricky for children to understand - I have many tutees on level 5 / 6 who still don't quite get that 12.3 = 12 3/10 and not 12 1/3/
  14. bestcoast

    bestcoast New commenter

    They are very tricky indeed! The children are aiming to be a Level 4 by the end of this year and after looking at the Level 4 assessment they will be doing, I'm worried that won't be possible! One of the questions involves the children converting fractions into decimals and vice versa. One of the decimals that needs to be converted into a fraction is 12.3 (surely this is far too difficult for a Level 4 pupil to do?)
    As you say, I am sure that there are many Y6 children that would find that incredibly difficult!

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