Multiplication Tricks Summary

Mental Math · Axiom Academy

SUMMARY Multiplication Tricks Summary The twelve shortcuts this unit hands you — what each one is really doing, and how the numbers tell you which to reach for. The work is in the looking, not the calculating. is two numbers an equal step either side of 50, so it is 2 , 500 - 4 = 2 , 496 — but only if you notice the pair before you start grinding. None of these is magic. Each one is a single identity in disguise: nine copies are ten copies minus one, a number ending in 5 squares to , and a symmetric pair collapses to m^2 - d^2 . The times table is one object, not a hundred facts. It mirrors down its diagonal, so 55 of its 100 cells carry all of it — and a row as regular as the 9s can be used to check an answer. Appending is not adding. Writing 25 after the 12 in 35^2 means twelve hundreds plus 25, so 1 , 225 ; adding would give 37, which is the square of nothing. A place holds exactly one digit. That one sentence is the whole difficulty in multiplying by 11, in cross multiplication, in the Vedic ripple and in every Trachtenberg card — whatever will not fit moves one place left and is added there. When no pattern shows up, cut. The distributive property always works: reach 7 × 48 out to , then hand back the two extra sevens, 350 - 14 = 336 . Estimate before you commit. tells you the answer's size in a second, and any slip large enough to matter breaks it. Core Concept Same Front, Ones Summing to 10

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