Mental Multiplication

Mathematical illiteracy is nothing to brag about with statements like, "I can never
balance my checkbook" or "I hate anything to do with math." Indeed, it's a pity
when department and grocery store cashiers nowadays have trouble counting out
your change if their computer register goes down. Remember, you're never too old
to learn speed mathematics. Take the example of Baron Herbert de Grote who was
over 60 when he started actively working on mental calculations and at the age of 82
was in the Guiness Book of World Records for his record breaking calculations.
To learn speed multiplication, first practice with adding zeros. For example 800
times 400 has 4 zeros that are simply added to the product of 32 making 320,000.


x 400


Now practice with the following until it becomes automatic:

90x30 50x60 300x70 540x80 2300x500 3000x2000 6000x200

Even though this seems real easy, it must be mastered and become second nature
to you before tackling what comes next. One of the consistent findings that
researchers have discovered about lightning calculators is that they multiply from left
to right and store only one fact away at a time. This is done in a 'moving' fashion so
fast that often calculators cannot explain the procedure until they're given a complex
computation that slows them down just enough to let them actually "watch" the
mental process in motion. Their conscious self actually watches their subconscious
self whiz through the calculation in a time distorted fashion (review "Exercise -- Time
Distortion"). The process of lightning calculating has simply become automatic to
As with any skill, regular practice brings you proficiency. You can actually learn
to creatively have fun playing with numbers. Look for ways to play with numbers
every day. For example, multiply how many people go into a building in one minute
X 60 to get an hourly traffic guesstimation.
As a right brain faculty, speed multiplication involves a reverse process of calcu-
lating from left to right, as opposed to left brain calculating of right to left. You will
sometimes find that you can encourage the right brain into performing calculations if
you first engage your left brain in a talking or writing mode.

The problem 349 times 462 is solved thus:

300 x 400 = 120,000

300 x 60 = 18,000 138,000

300 x 2 = 600 138,600

400 x 40 = 16,000 154,600

400 x 9 = 3,600 158,200

40 x 60 = 2,400 160,600

40 x 2 = 80 160,680

60 x 9 = 540 161,220

9 x 2 = 18 161,238

When a problem is visibly written, some lightning calculators use criss-cross
multiplication. This is a right to left method that can be used in a mental way as well.
The problem 349 times 462 becomes: