Multiplication Tricks
SOL 4.7
Basic Facts Tricks:
· Anything Times 0 = 0
o 5 X 0 = 0
o 18,574 X 0 = 0
· Anything Times 1 = Itself
o 5 X 1 = 5
o 18,574 X 1 = 18,574
· Anything Times 2 is Doubled
o 5 X 2 = 10
o 20 X 2 = 40
· Times 3 = count by 3’s
· Times 4 = Double the number and double it again.
o 5 X 4 = 5 doubled is 10 and doubled again is 20.
· Times 5 = count by 5’s
· Times 6, 7= Just MEMORIZE
· Times 8 = Doubled, Doubled and Doubled (3 times)
o 5 X 8 = 5 doubled = 10
o 10 doubled = 20
o 20 doubled = 40
· Times 9 = Use hand trick. Hold both hands flat, Fold the finger that is being multiplied by 9. Look at the fingers to the LEFT – that’s the first digit, Look at the fingers on the RIGHT – that’s the second digit.
· Times 10 = Just add 0 to the digit.
o 6 X 10 = 60
· Times 11 = That number twice, until 10’s
o 11 X 7 = 77
· Times 11 any above 11 = Since you are multiplying eleven by 12, your answer will have a 2 on the right and a 1 on the left and the SUM of 1 and 2, which is 3, in the middle. Just think of it as pulling the 1 and 2 apart and inserting their SUM in the middle.
o 11 X 12 = 1 2,
o sum of 1+2 =3,
o put 3 in the middle = 132
· Times 12 = Just MEMORIZE!
Try these…
Multiple Using Front End Estimation
23x 14 / 377
x 22 / 851
x 188 / 314
x 74 1 / 158
x 314
3245
x 372 / 303
x 291 / 676
x 33 / 778
x 562 / 611
x 497
Multiply Using Compatible Numbers
872
x 69 / 802
x 69 / 878
x 72 / 277
x 12 / 910
x 81
39
x 39 / 82
x 18 / 48
x 41 / 80
x 39 / 60
x 78
Multiply using your own method
94
x 24 / 18
x 85 / 37
x 19 / 28
x 48 / 23
x 45