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.
Example: 23? 27=?
Solution: 2+ 1=3
2? 3=6
3? 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
1? 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=?
Answer: 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: 13 bit is 3.
3? 3+2= 1 1
3? 2+6= 12
3? 6= 18
13? 326=4238