1, tailing method
That is, the mantissa of each number is removed and the whole number is calculated.
For example, Dongfang Travel Service organized several tour groups during the 11th period. The situation is: Lijiang 524, Huangshan 208, Great Wall 602, Jiuzhaigou 365,438+09, Emei Mountain 265,438+09. How many people did the travel agency receive during the eleventh period?
Remove the mantissa and add the whole hundred numbers to get: 524+2084602+3104219 ≈ 500+200+600+300+200.
= 1800 people.
2, into the law
That is, the highest digit of each number plus 1 is calculated as an integer of ten.
For example: 28+15+7+24 ≈ 30+20+10+30 = 90.
3. Rounding method
That is, the mantissa is less than or equal to 4, and the mantissa is equal to or greater than 5. People can go in and take ten or a hundred teachings to calculate.
For example, "1.8 Jin of apples, how much should I pay per Jin of 420 yuan"? The estimated value is 42× 1, 8≈4×2=8 (yuan).
Knowledge points to be mastered in third grade estimation
1, the estimate is only a rough figure, not an accurate result.
2. Estimation method: First, consider a multi-digit as the nearest integer of ten, one hundred and one thousand, and then multiply it by one digit.
3. Write ""(about equal sign) in the estimated horizontal style, and add "about" to the answer. Such as 398×6≈ (398 is 400),
203×5≈ (203 is 200), 347×2≈ (347 is 350) and 996×7≈ (996 is 1000).
4. When estimating, estimate multiple numbers, not one number.