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 numbers 100 to get:
524+2084602+3 1042 19
≈500+200+600+300H20
1800 (person).
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. Four-room sealing 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).
4. Ten methods add up
Put the related teaching together and add it up to 10. For example:
17+8+ 12424
( 17+ 12)+(8+24)
≈30+30
=60
5, a part of the whole
That is, divide a large whole into several parts on average, and calculate an integer according to the number of parts. For example, to estimate the number of spectators in the stadium, first divide each stand into several parts, count the number of people in one part, then estimate the educational background of one stand, and finally calculate the number of people in the whole stand according to several spectators.