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← Dividing Fractions Word Problem

U02_L2_T3_we5 Dividing Fractions Word Problem

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Showing Revision 1 created 04/17/2011 by brettle.

  1. A baby's T-shirt requires 4/5
    yards of fabric, or 4/5 of a
  2. yard of fabric.
  3. How many T-shirts can be
    made from 48 yards?
  4. So what we want to do is we
    essentially want to say how
  5. many groups of 4/5 of a yard
    can we make with 48 yards?
  6. So you literally view this as
    we want to take 48 yards and
  7. divide it into groups of 4/5
    of a yard, and say how many
  8. groups are there?
  9. Because each of those
    groups can make
  10. one to baby's T-shirt.
  11. If you give me 4/5 of a yard,
    one baby's T-shirt, so the
  12. number of groups of 4/5 is the
    number of babies' T-shirts.
  13. Now, when we divide by a
    fraction, we just have to
  14. remember that that is the same
    thing, that is completely
  15. equivalent to multiplying
    times the
  16. reciprocal of the fraction.
  17. So if we have 4/5 here,
    that'll be 5/4, the
  18. reciprocal.
  19. Now, you still might say, hey, I
    have a whole number here and
  20. a fraction, and you just have
    to remember any whole number
  21. can be written as a fraction.
  22. This is the same thing
    as 48/1 times 5/4.
  23. Now, we could just multiply it
    out at this point and figure
  24. out what 48 times 5 is and
    that'll be over 4, but that'll
  25. get big numbers and it'll be
    hard to kind of divide and all
  26. that, but we could divide at
    this stage right here.
  27. We could divide the numerator
    and the denominator by 4.
  28. Or we could say, look, this is
    going to be equal to 48 times
  29. 5, whatever that is, over 4.
  30. Now, let's divide the
    numerator by 4.
  31. Well, we could divide 48 by 4,
    and we will get to 12, and
  32. whatever we did to the
    numerator, we have to do to
  33. the denominator, so if we
    divide 4 by 4, we get 1.
  34. So then we're left with 12 times
    5, which is equal to 60.
  35. 12 times 5, which is equal to
    60/1, which is the exact same
  36. thing as 60.
  37. So you can actually make 60
    children's or babies' T-shirts
  38. from 48 yards if each of
    them use 4/5 of a yard.