Wang Dongdong, a lecturer and psychological counselor of the Central Plains Focus Team, has continuously recorded 1599 days (2022.4.26) when the clouds turned cloudy
The twenty-sixth day of the third month of the lunar calendar is the first month of the year of the tiger in Renyin. Jiyou day, the second day of the second period of Grain Rain. < /p>
I accidentally saw a teacher teaching students (I think most of them are parents) to do quick calculations. I joined in with great interest. Haha, I learned several quick calculation methods. I don’t know how long I can remember them. , as long as I can learn it at that time, haha, I have lower and lower requirements for myself. Write it down first and then talk about it.
1. Multiply a dozen by a dozen
Formula: multiply the head by the head, and multiply the tail by the tail to get the number.
Example: 15*19=145
1*1=1, 5*9=45, directly get 145, haha, so fast.
Try a set: 18*16=148; 12*19=118
2. Multiply dozens of one by dozens of one
Formula: Head The first word is written as the front, the first word is added to the middle station, and the last word is written as the last word.
Example: 51*81=40131
5*8=40 (write the front), 5+8=13 (write immediately after 40) 1*1=1 ( Write at the end, after 13)
31*61=1891
3. Two-digit multiplication
Formula: Multiply the head and write the front, tail Write the multiplication on the back, the multiplication on the inside in the middle, the multiplication on the outside on the bottom, and add up the total to get the number.
Example: 56*48=2688
5*4=20 (write the front), 6*8=48 (write the back)? 2048
6 *4=20 (write in the middle), 5*8=40 (below)
? 2 0 4 8
2 0
4 0
————————
? 2 6 8 8
56*47=2632
2042
< p> ? 24? +? 35
------------------
2632
4. Multiply a hundred and a few by a hundred and a few
Formula: The first number plus the last number and the last number are written in the front, and the last number multiplied by the last number is written in the back.
Example: 106*108=11448
106+8=114 (the first number plus the last number)
6*8=48 (the last number multiplied by the last number) )
Result: 11448 (write in front-to-back order)
? Isn’t it very simple and interesting? Practice it repeatedly until you can calculate the answer subconsciously.