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Daft fraction question...

Discussion in 'Mathematics' started by MrsK2806, Aug 13, 2011.

  1. Could someone please confirm if I've got this right?
    7 4/9 - 2 5/9 = 4 8/9

    Changed to an improper fraction: 67/9 - 23/9
    Original answer: 396/81
    Changed to mixed number: 4 72/81
    Cancelled down to: 4 8/9

    There are no answers on the worksheets I am working from and I just need to check that I've grasped the concepts.
     
  2. Could someone please confirm if I've got this right?
    7 4/9 - 2 5/9 = 4 8/9

    Changed to an improper fraction: 67/9 - 23/9
    Original answer: 396/81
    Changed to mixed number: 4 72/81
    Cancelled down to: 4 8/9

    There are no answers on the worksheets I am working from and I just need to check that I've grasped the concepts.
     
  3. DM

    DM New commenter

    That's correct but you made it a bit too hard.
    When you had 67/9 - 23/9 you already had a common denominator so you can just subtract the numerators to get 44/9 and then make it into a mixed number.
     
  4. Ha, I didn't even notice the common denominator I was so set on doing it the way I've learnt from the disc! Thanks DM!
     
  5. That looks right to me. [​IMG]
    Not sure why you went from ninths to 81ths though! Since the denominators are the same, you can subtract 67/9 - 23/9 = 44/9 just looking at the numerators (67 - 23).
    Then change back to a mixed number as you have done.
    If you want to check, do the numbers and fractions separately: 7 minus 2 is 5 and 4/9 minus 5/9 is -1/9. So take 1/9 off 5 and you get 4 8/9. But for some reason you're not allowed to do it that way...
     
  6. DM

    DM New commenter

    Avatar for you Myttin_da:
    [​IMG]
     
  7. Another one [​IMG]
    Line PQ is parallel to line RS
    If angle PQR is equal to 36 degrees
    What is the size of the angle QRS?
    Give a reason for your answer.
    (the picture is of a slightly stretched Z shape if that makes sense)
    I think it's 36 degrees and the reason is that they are corresponding angles. I expect I'm probably wrong and they are alternate angles but the whole Z and F thing confuses me!
     
  8. DM

    DM New commenter

    It is 36 degrees because they are alternate. Look for the Z shape! Trace from P to Q to R to S with your finger.
     
  9. And yet another, sorry!
    The diagram shows a shape, made from a semi-circle and a rectangle. The diameter of the semi-circle is 13cm. The rectangle is 17cm by 13cm.
    Calculate the area of the shape. Give your answer correct to 3 S.F.
    Answer 271.63 - Is this then 272? And is the answer itself right?

    Sorry maths teachers, I know you're supposed to be on holiday!
     
  10. Yes, 271.63 to 3 s.f. is 272.

    Unfortunately your answer is incorrect.

    Area of rectangle = 17 x 13 = 221 cm^2

    Area of semicircle = 0.5 x ?r^2 = 0.5 x ? x 6.5^2 = 66.366 cm^2

    Therefore area = 221 + 66.366 = 287.366 = 287 cm^2 to 3 s.f.
     
  11. I don't even know how I got the figure of 272! I just did the sum again, the same way I thought I did last night, and got the same answer as you. I think it must have been a case of brain freeze so late at night! Thank you for your reply.

     
  12. DM

    DM New commenter

    You seem to be doing well MrsK. Keep it up.
     
  13. <font face="Calibri">If you are working from the MathsWatch worksheets, the answers are on the disk too. When MathsWatch opens on your PC it goes to a screen which gives you the options on the right hand side of - Modular, Worksheets, Functional skills, and Help, if you select &lsquo;Help&rsquo;, from there you should see &lsquo;Answers to worksheets&rsquo;. </font>
    <font size="3">Blue.</font>
     
  14. Hello everyone again.
    Could I beg for help once more please? I'm really struggling with the simplifying and expanding concept. I'm getting about 50% of the questions correct but when it mixes the plus and minus signs I start to get it wrong every time.
    For example, I tried to expand and simplify: 6(x - 3y) - 2(2x - 5y) and ended up with the answer: 2x - y. I know now that the answer is 2x - 8y but am I missing a fundamental rule somewhere about which way to use the + and - signs when trying to solve it?

    Some help would be much appreciated! I'm on the final countdown now, less than 35 hours to go now.
     
  15. mmmmmaths

    mmmmmaths New commenter

    Split it into two parts the first bracket expands to 6x-18y

    the second bracket 2(2x-5y) expands to 4x-10y

    This second expression has to be subtracted from the first so you have:

    (6 x -18 y)-(4x-10y) = 6 x-18y-4x+ 10 y


    this will give give the answer required

    Post again which part of this you want explaining further
     
  16. Thank you - I can see that answer now. However, 5(3p + 2) - 2(4p - 3) gave me the answer 23p + 16. I know that's wrong and the answer is really 7p + 16. What is it though that dictates which sign you use for which section? I don't know if I'm making much sense but how can I tell whether I am adding 10 and 6 or subtracting because there are lots of signs here to confuse me.
    I'm really sorry if I seem stupid. I used to be good at maths and have found that I'm enjoying doing this but it has been many years and English has been my life for so long that the concept of maths is hard to grasp.
     
  17. mmmmmaths

    mmmmmaths New commenter

    The first bracket 5(3p+2) = 15p+ 10

    The second bracket 2(4p-3) =8p - 6

    The -sign that comes between these means subtract the second expression from the first


    (15p+10) - (8p-6) =15p+10-8p+6=15p plus 10 subtract 8p plus 6


    So with the p's you have 15p subtract 8p

    then you have plus 10 plus 6

    Does this help?
     
  18. Yes I think so! And am I right in thinking that if it's two minus signs (i.e. in this example if it was -8p-6) it would be a plus? Or is that only in other expressions?
    One more question for you mmmmmaths if you don't mind? I've just come to the section on the CD-Rom where I'm asked to expand and simplify and I just don't have a clue.
    (x + 1)(x + 2) - the answers tell me that it's x^2 + 3x + 2 but I got 2x + 3. How are they getting to that answer and where am I going wrong?
     
  19. mmmmmaths

    mmmmmaths New commenter

    I think I understand your first question.

    If it had been this question instead 5(3p+2)-2(-4p-3) =15p plus 10. Plus 8p. Plus 6

    so you would then get 23p+16


    Your next one is very different. There are two sets of brackets with no sign between them. This means that the two brackets are multiplied together. So you multiply everything in the second bracket b everything in the first bracket.

    Example (x+5)(x+2) = x multiplied by x PLUS x multiplied by 2 PLUS 5 multiplied by x PLUS 5 multiplied by 2

    So you get x^2 + 2x + 5x + 10

    you can simplify the x terms to get the answer X^2+7x+10
     
  20. Thank you so much for taking the time to try and decipher my ramblings. I'm going to call it a night and review the answers you've given me tomorrow so I can hopefully figure them out properly. I'm sure there are rules to this stuff that have to be followed but I just can't see them clearly at the moment.
    Thank you for all of your help. I'm sure I'll be taking up more of your time tomorrow evening but if you feel like telling me to *** off I would completely understand!
    Thanks,
    Kate
     

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