【正文】 ability of calculation.（2）記憶一些常用數(shù)據(jù)和巧算方法。像20以內(nèi)的加減法、表內(nèi)乘法、120的平方數(shù)等，都要求學(xué)生熟記，達(dá)到脫口而出的程度。同時(shí)，經(jīng)常教學(xué)生一些巧算的方法，也可使其計(jì)算速度大大提高。如：一個(gè)數(shù)與“11”相乘，“兩邊一拉，中間一加，滿十向前一位進(jìn)一”；一個(gè)數(shù)與2125相乘，都可以運(yùn)用巧算方法：(2)memory and some monly used data coincidence counting addition and subtraction, multiplication table within 20, 120 square number, etc., require students to memorize and to the point of blurt the same time, often teach students some clever calculate way, also can make its calculation speed is greatly as: is multiplied by a number from “11”, “on both sides of a pull, a middle, ten a into a” forward。With a number is multiplied by 5, 25, 125, can use opportunely calculate method:245=24247。210* 24 present 2 * 5 = 1032425=324247。4100= 324 present 4 x 324 x 324409125=408125+125=408247。81000+125409 * 125 = 408 * 125 + 125 = 408 present 8 x 1000 + 125還有一些除法試商法：差數(shù)試商法、同頭無除商八九法（當(dāng)被除數(shù)和除數(shù)最高位上的數(shù)字相同時(shí)，俗稱“同頭”，被除數(shù)的前幾位比除數(shù)小，且除數(shù)與被除數(shù)次高位上的數(shù)的差不超過最高位時(shí)，可直接用八與九試商）、中數(shù)試商法、折半試商法等等，這些都是學(xué)生快算所必須掌握的基本方法。Try some division mercial law: differential try to mercial law, with the head in addition to business method(when the Numbers on the dividend and the divisor that high phase at the same time, monly known as the “head”, dividend top is smaller than the divisor, and the divisor and dividend the number of times on the high error is less than the highest level, can be directly used eight and nine test quotient), median try mercial law, binary and mercial law, and so on, these are students quick is necessary to master the basic 、理解算理，提倡算法多樣化要使學(xué)生會(huì)算，必須要使其明確算理，這就要求教師對(duì)算法和算理的教學(xué)必須正確，因?yàn)榈谝挥∠蠓浅Ｖ匾?，第一次講錯(cuò)以后就很難改掉。記得一位心理學(xué)家說過：首次感知新知識(shí)時(shí)，進(jìn)入大腦的信息可以有受前攝抑制的干擾，能在學(xué)生的大腦皮層留下深刻的印象。但如果首次感知不準(zhǔn)確，那么造成的不良后果在短期內(nèi)是難以清除的。因此，教師必須充分備課，選擇最優(yōu)方案，以期達(dá)到良好的教學(xué)效果。To make the student union, must make it clear to calculate, this requires teachers to the algorithm and the principle of teaching must be correct, because the first impression is very important, for the first time speak wrong, it is hard to remove it a psychologist said: first perception of new knowledge, proactive inhibition of information into the brain can be affected by the interference, can leave deep impression in students39。 brain if the first perception is not accurate, the adverse consequences in the short term is difficult to , the teacher must fully preparation, select the optimal scheme, in order to achieve good teaching ，要提倡算法多樣化。算法多樣化不是要求每個(gè)學(xué)生都用多種方法解決同一問題，而是要鼓勵(lì)學(xué)生獨(dú)立思考，用適合自己的方法解決，有能力的可以運(yùn)用多種方法，沒有這種需求的學(xué)生只用一種即可。提倡算法多樣化，也要注意方法的優(yōu)化，對(duì)于學(xué)生想出的每一種正確方法都給予肯定，說服學(xué)生放棄自己的落后繁瑣觀點(diǎn)，去遵循優(yōu)秀、簡(jiǎn)潔的方法，這樣才能使自己的思維能力不斷提高。特別要對(duì)中、高年級(jí)提出的每一種算法，可讓其自己說明算理，以防止其“知其然，不知其所以然”，同時(shí)起到培養(yǎng)學(xué)生邏輯思維和口頭表達(dá)能力的作用。In students is clear, on the basis of to promote diversity algorithm isn39。t required that every student(should)use a variety of methods to solve the same problem, but rather to encourage students to think independently and solve with suitable methods, ability can use a variety of methods, without the need of students in a algorithm diversity, also want to pay attention to the optimization method, for students to e up with every kind of right way to give affirmation, persuade students give up their backward trival, to follow the outstanding, simple method, so as to make their thinking ability constantly for middle and senior each kind of algorithm, can calculate, make its own instructions in order to prevent the “l(fā)earning, don39。t know why”, at the same time cultivate students39。 logical thinking and the role of oral expression 、重視估算，教給方法Third, the value estimate, teach method在日常生活和生產(chǎn)實(shí)際中，某些計(jì)算和測(cè)量的結(jié)果無法得到或沒有必要得到精確計(jì)算結(jié)果或判斷時(shí)，就要用到估算的方法。如一個(gè)房間的大小、從家到學(xué)校的距離、某樓房的高度、有經(jīng)驗(yàn)有漁民判斷某片水域里魚的數(shù)量等。因此，重視學(xué)生估算能力的培養(yǎng)，不僅可以使學(xué)生的思維更加靈活，而且對(duì)學(xué)生的直覺思維能力的培養(yǎng)有很大的幫助。同時(shí)，加強(qiáng)估算，可以加深學(xué)生對(duì)數(shù)字的認(rèn)識(shí)，促進(jìn)數(shù)感的培養(yǎng)，增強(qiáng)應(yīng)用數(shù)學(xué)的意識(shí)，提高解決實(shí)際問題的能力。在教學(xué)中，我經(jīng)常性地貫穿一些估算的技巧和方法：In our daily life and production practice, some calculation and the measurement result can39。t get or there is no need to get the precise result or judgment, is employed to estimate as the size of a room, the distance from home to school, a building height, experienced fishermen who judge a number of fish in the water, to the cultivation of students39。 ability