Here are some simple mathematical oral calculation methods, and the formulas are very important.

1 .10 times 10:

Formula: head joint, tail to tail, tail to tail.

For example: 13× 15=? Solution:/kloc-0 /×1=13+5 = 83× 5 =1513×15 =195.

Note: Numbers are multiplied. If two digits are not enough, use 0 to occupy the space.

2. 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 of1/kloc-0 /× 23125 = 254375. Note: If the total is ten, you must enter one.

3. 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.