24*24=200*(2+ 1)+4*6=624

34*36=300*(3+ 1)+4*6= 1224

.......

2, there are the above rules, there are

124 *126 =1200 * (12+1)+4 * 6 =15600+24 =15624.

3, in the same way, more than ten digits (hundreds of thousands, etc. ) are the same, and the sum of single digits is equal to 10. Multiplication with more than two digits can have such a rule:

( 10m+a)*( 10m+b)= 100 * m(m+ 1)+a * b

For example:

67 * 63 = 600 * (6+1)+3*7 = 4221(6 * 7 = 42 is a hundred digits, 3 * 7 is a single digit, or as a result of directly reporting 3 * 7, it is put after 42 to form a multi-digit).