Tuesday, February 15, 2011

Different ways for multiplication

Another way to multiply just over 100
  • 103 x 104 = 10712 The answer is in two parts: 107 and 12,
    107 is just 103 + 4 (or 104 + 3),
    and 12 is just 3 x 4.
  • Similarly 107 x 106 = 11342 107 + 6 = 113 and 7 x 6 = 42
  • Method for multiplying numbers where the first figures are the same and the last figures add up to 10.
    • 32 x 38 = 1216 Both numbers here start with 3 and the last
      figures (2 and 8) add up to 10.

      So we just multiply 3 by 4 (the next number up)
      to get 12 for the first part of the answer.

      And we multiply the last figures: 2 x 8 = 16 to
      get the last part of the answer.

      Diagrammatically:
    • And 81 x 89 = 7209

    • Multiplying a number by 11.
      • To multiply any 2-figure number by 11 we just put the total of the two figures between the 2 figures.
      • 26 x 11 = 286 Notice that the outer figures in 286 are the 26
        being multiplied.
        And the middle figure is just 2 and 6 added up.
      • So 72 x 11 = 792

2 comments:

  1. can we do questions of probability through vein diagram?

    ReplyDelete
  2. yes , you can apply vein diagram concept instead of formula for three sets.

    ReplyDelete