How many people did * * * receive during the period? After the mantissa is removed, hundreds of integers are added to get 524+208+602+310+219 ≈ 500+200+600+300+20 =1800 (person).
2, into the law. That is, the highest digit of each number plus 1 is calculated as an integer of ten. Such as: 28+15+7+24 ≈ 30+20+10+30 = 90.
3. Rounding method. That is, mantissa is less than or equal to 4, mantissa is equal to or greater than 5, and it is calculated by integer ten or integer hundred. For example, "apples are 4 per kilogram. 20 yuan, 1. How much is 8 kilograms of apples? " The usage estimate is 4. 2× 1。 8≈4×2=8 (yuan).
4. Ten methods add up. That is, the related figures add up to close to 10. Such as17+8+12+24 = (17+12)+(8+24) ≈ 30+30 = 60.
Example: a set of tickets and tickets. 49 yuan, Level 4 needs a set of tickets for 104. How much do you need to prepare?
Method 1: 49× 104≈5000 (yuan) 50* 100.
Method 2: 49× 104≈4500 (yuan) 45 * 100.
Method 3: 49× 104≈5500 (yuan) 50 * 1 10.
Method 4: 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 third estimation method, because 49 is regarded as 50 and 104 as 1 10, both numbers are too large, so the estimation result of 50×10 is equal to 5500, which is definitely greater than 49×/kloc-0.
In the fourth 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 accurate value. I think the second method is not good, because 49 is 45 and 104 is 100, both numbers are too small, so the estimated result of 45× 100 is equal to 4500, and it is definitely not enough to bring 4500 yuan.