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long - multiplication .ppt

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					       Oh no! I can’t do long
       multiplication. What
         am I going to do?




    Don’t panic!
Take it step by step
  and follow this
     example.
23 x 14


   When multiplying these two numbers
      together, it is easier to put
           them into a grid.
             The first thing to do is
23 x 14    partition the numbers into
                  tens and units.


      20          3

 10


 4
                Multiply the number above

23 x 14
              the box with that on the left,
            writing the answer inside the box,
                     as shown below.

      20              3

 10   200             30


 4    80              12
                The next step is to add up
     23 x 14   the rows, putting the answer
                 in the boxes on the right.


       20      3

10    200      30           230


4      80      12            92
               Now add up the totals on the
     23 x 14    right to give the answer.



       20      3

10    200      30           230


4      80      12            92

                            322
  Now you can work out multiplication
using the grid method, you will find long
           multiplication easy!



             This is a little different
             from the grid method,
               as the numbers are
              set out in columns…
51 x 42
      becomes
                  51
                x 42
                                    Remember what

 51 x 42                      51
                                     we did using
                                   the grid method?

                            x 42
The first thing to do, is
 multiply the tens of the
top number with the tens
 and units of the bottom
          number.
51 x 42                      51
                          x 42
         50 x 40           2000
         50 x 2             100

Always write down the
multiplication you have
 worked out next to
      the answer.
                 Next, multiply the

51 x 42         51
                   units of the top
                 number by the tens
                  and units of the
             x 42  bottom number.


   50 x 40    2000
   50 x 2      100
                     Don’t forget to

51 x 42         51
                     write down the
                      multiplication
                       next to the
             x 42        answer.


   50 x 40    2000
   50 x 2      100
    1 x 40      40
    1x 2         2
                     The final step is

51 x 42         51
                      to add up the
                         column of
                     numbers and put
             x 42      the total at
                       the bottom.

   50 x 40    2000
   50 x 2      100
    1 x 40      40
    1x 2         2
              2142
Try using long multiplication
       to work out…


        25 x 62
25 x 62
     becomes
                 25
               x 62
 25 x 62                       25
                             x 62
                x
                x
          Remember:
The first step is to multiply the
tens of the top number with the
  tens and units of the bottom
            number.
25 x 62          The next step is to

                25multiply the units
                  of the top number
             x 62  by the tens and
                 units of the bottom
   20 x 60    1200     number.


   20 x 2       40
      x
      x
25 x 62           25
                       Now add up
                        the totals
                         and put
               x 62    them at the
                         bottom.
   20   x 60    1200
   20   x 2       40
    5   x 60     300
    5   x 2       10
25 x 62           25
               x 62
   20   x 60    1200
   20   x 2       40
    5   x 60     300
    5   x 2       10
                1550
You can now work out
  calculations using
 long multiplication.

				
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posted:5/22/2013
language:simple
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