1 .10 times 10:
Formula: head joint, tail to tail, tail to tail. For example: 12× 14=? Solution: 1× 1= 1.
2+4=6 2×4=8
12× 14= 168
Note: Numbers are multiplied. If two digits are not enough, use 0 to occupy the space.
2. The heads are the same and the tails are complementary (the sum of the tails is equal to 10): Formula: after a head is added with 1, the head is multiplied by the head and the tail is multiplied by the tail. For example: 23×27=? Solution: 2+ 1 = 32× 3 = 63× 7 = 2 1.
23×27=62 1
Note: Numbers are multiplied. If two digits are not enough, use 0 to occupy the space.
3. The first multiplier is complementary, and the other multiplier has the same number: formula: after a head is added with 1, the head is multiplied by the head and the tail is multiplied by the tail. For example: 37×44=? Solution: 3+ 1=4
4×4= 16
7×4=28
37×44= 1628
Note: Numbers are multiplied. If two digits are not enough, use 0 to occupy the space.
4. Eleven times eleven:
Formula: head joint, head joint, tail to tail. For example: 2 1×4 1=? Solution: 2× 4 = 8 2+4 = 6/kloc-0 /×1=1.
2 1×4 1=86 1
5. 1 1 times any number:
Formula: head and tail do not move down, middle and pull down. For example: 1 1×23 125=? Solution: 2+3=5 3+ 1=4 1+2=3.
2+5=7
2 and 5 are at the beginning and end respectively.
1 1×23 125=254375
Note: If you add up to ten, you will get one.
6. Multiply a dozen by any number:
Formula: The first digit of the second multiplier does not drop, the single digit of the first factor multiplies each digit after the second factor, and then drops. For example: 13×326=? Solution: the position 13 is 33× 3+2 =113× 2+6 =123× 6 =18.
13×326=4238
Note: If you add up to ten, you will get one.