2. One-to-one method: One-to-one method is to add 1 to the last bit of the reserved part after removing redundant figures. The approximation thus obtained is a residual approximation (i.e., greater than the exact value).

For example, a sack can hold 200 Jin of wheat and there are 880 Jin of wheat. How many sacks do you need to wrap it? When 880 is divided by 200, the quotient is 4, and the remainder is 80, that is, 4 sacks are not enough, and 5 sacks are needed.

3. Truncation method: Truncation method is a commonly used mathematical method, which removes the decimal part of a number and takes its integer part, and its value is approximate (that is, less than the exact value), which is often used in life.

4. Quantity unit estimation method: use real-life objects to perceive the quantity unit and size of actual empirical data.

Extended data:

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Related examples:

A set of tickets and tickets 49 yuan, the fourth grade needs a 104 set of tickets, how much do you need to prepare?

Method 1: 49× 104≈5000 (yuan) 50* 100.

Method 2: 49× 104≈5500 (yuan) 50 * 1 10.

Method 3: 49× 104≈5250 (yuan) 50 * 105?

The first estimation method is very convenient, because 49 is regarded as 50, 104 is regarded as 100, and 50× 100 equals 5000.

In the second estimation method, because 49 is regarded as 50, and 104 is regarded as 1 10, the estimated result of 50×10 is equal to 5500, which is definitely greater than 49× 104. There are also

In the third estimation method, because 49 is regarded as 50 and 104 as 105, both numbers are a little too big, so the estimation result of 50× 105 is equal to 5250, which is very close to the exact value.