Tutorial 2
Using VERTICALLY AND CROSSWISE you do not need to the multiplication tables beyond 5 X 5.
  • Suppose you need 8 x 7

    8 is 2 below 10 and 7 is 3 below 10.
    Think of it like this:

    The answer is 56.
    The diagram below shows how you get it.

You subtract crosswise 8-3 or 7 - 2 to get 5,
the first figure of the answer.
And you multiply vertically: 2 x 3 to get 6,
the last figure of the answer.

That's all you do:

See how far the numbers are below 10, subtract one
number's deficiency from the other number, and
multiply the deficiencies together.

  • 7 x 6 = 42

    Here there is a carry: the 1 in the 12 goes over to make 3 into 4.

Here's how to use VERTICALLY AND CROSSWISE for multiplying numbers close to 100.

  • Suppose you want to multiply 88 by 98.

    Not easy,you might think. But with
    VERTICALLY AND CROSSWISE you can give
    the answer immediately, using the same method
    as above.

    Both 88 and 98 are close to 100.
    88 is 12 below 100 and 98 is 2 below 100.

    You can imagine the sum set out like this:

    As before the 86 comes from
    subtracting crosswise: 88 - 2 = 86
    (or 98 - 12 = 86: you can subtract
    either way, you will always get
    the same answer).
    And the 24 in the answer is
    just 12 x 2: you multiply vertically.
    So 88 x 98 = 8624