6.64+3.3 Vertical:

9.4+6 Vertical:

Extended data:

Law of addition:

One-digit addition: When two one-digit numbers are added, the sum can be obtained directly by counting.

The result of adding two one-digit numbers is usually compiled into an addition table.

Multi-digit addition: the addition of numbers on the same digit; One number adds up to ten, then go to the previous number and enter one.

Multiple digits plus multiple digits, you can first write two multiple digits as the sum of different counting units.

Then, according to the arithmetic of addition and the law of one-digit addition, the numbers with the same counting unit are added respectively.

Additive properties of real numbers;

Add two numbers with the same sign, use the same sign as the addend, and then add the absolute values.

Add two numbers with different signs, take the sign of the addend with the largest absolute value, and subtract the smaller absolute value from the larger absolute value.

Adding 0 to any number still gets the original number.