天哪，一上网就让我考数学？

赶快去看今天儿子把数学课本带回家没有，这小子不怕重，背回来了。赶快打开看书上有没有例题啥的。比较接近的逮到一例如下：

To estimate sum: 5.53 + 2.32

Way 1: use front-end estimation. First: add the digits in the greatest place 5+2=7.  Second: adjust.  Look at the digits in the next greatest place 5.5+2.3= 7.8.

Way 2: use rounding.  Round to the nearest whole number.  Then add. 5.53-->6; 2.32-->2.  6+2=8.

Note that the first front-end estimate, 7, is an underestimate, while the rounded estimate, 8, is an overestimate.  The actual sum, 7.85, is between the underestimate and the overestimate.

Source: Math, Houghton Mifflin, p 11.

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• 老美就是喜欢p大点事弄的很复杂，烦 -clipmom- ♀ (0 bytes) () 01/10/2011 postreply 19:35:47