Recite the multiplication formula before 3 in stages first. Get one by one; One two gets two, two two gets four; One three gets three, two three gets six, and three three gets nine.

Analysis: A 1 is one, a 2 is two, 22 is four, 1 3 is three, 23 is six and 33 is nine.

Fourteen gets four, twenty-four gets eight, 3412,446.

Fifteen gets five, twenty fifty, three five fifteen, four five twenty, five five twenty-five.

Analysis: the formula from one to five is easier to understand. Therefore, after learning the formula from one to five, we must first consolidate the formula from one to five and recite the formula from one to five.

The formula of 6789 should be studied separately.

16 got 6,262,368,4624,5630,6636.

17 is 7,274,3721,4728,5735,6742,7749.

18 has 8,286,3824,48312,5840,68418,78516,8864.

Nine-tenths, 298,3927,4936,59415,6954,79613,8972,9981.

In fact, there is a rule in the formula of 9, that is, 19 gets 9, followed by the numbers of 29, 39, 49 1 to 99, and the numbers in the unit and the tenth place add up to 9, 18, 27, 36, 45, 54, 63, 72.