✔ 最佳答案
大大你好！
即然你懂第二題了，我就不多說了。
1249 / 256 + 489 / 67
約= 1250 / 250 + 490 / 70
= 5 + 7
= 12
所以，1249 / 256 + 489 / 67 約等於 12。
你可以看看 compatible number 的定義的，有一條例子喲 ~
Compatible Number
Definition of Compatible Number
Compatible numbers are numbers that are close in value to the actual numbers and easy to add, subtract, multiply, or divide mentally.
They are useful in estimating the sum, difference, product, or quotient.
Examples of Compatible Number
Estimate 13 3.6.
To estimate the quotient, choose the compatible numbers 12 and 4 as 12 and 4 are compatible with each other. Also notice that 12 is closer to 13 and 4 is closer to 3.6.
http://www.northstarmath.com/SiteMap/CompatibleNumber.html
