### 數值估算的技巧

 ${\left({a}\right)}$ Reformulation strategy ${\left({i}\right)}$ Rounding off ${\left({i}{i}\right)}$ Using clustered value If the numbers involved in an estimation are close to each other, we can select a clustered value to represent them. ${\left({i}{i}{i}\right)}$ Using compatible numbers Compatible numbers are approximate value that make calculation easier. ${\left({b}\right)}$ Compensation strategy This method makes adjustment to the result of a rough estimation so that it is closer to the exact value. ${\left({c}\right)}$ Translation strategy This method rearranges the order of operations in a complicated expression so that the estimation can be simplified. ${\left({d}\right)}$ Taking larger or smaller approximations When isong estimation to solve real-life problems, we should determine whether to take larger or smaller approximations in order to obtain more useful estimates. Note:  1. To round up a number, we take an approximation which is slightly larger to replace the original number. 2. To round down a number, we take an approximation which is slightly smaller to replace the original number.

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