倒数能帮助我们解答各种代数方程。如果你需要将两个分数相除,用第一个分数乘以第二个分数的倒数就可以了。在解直线方程时也会用到倒数。
步骤
方法 1 的 3:
求分数或者整数的倒数
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/3\/3e\/Find-the-Reciprocal-Step-1-Version-3.jpg\/v4-460px-Find-the-Reciprocal-Step-1-Version-3.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/3\/3e\/Find-the-Reciprocal-Step-1-Version-3.jpg\/v4-728px-Find-the-Reciprocal-Step-1-Version-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
1
将分数上下颠倒就是它的倒数。“倒数”的定义其实很简单。只要"用1除以(某个数)"就能得到这个数的倒数。对于分数而言,倒数就是"上下颠倒"后得到的另一个分数。[1]
- 比如,3/4的倒数是4/3。
- 任何数字和它的倒数相乘结果都是1。
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/5\/5d\/Find-the-Reciprocal-Step-2-Version-3.jpg\/v4-460px-Find-the-Reciprocal-Step-2-Version-3.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/5\/5d\/Find-the-Reciprocal-Step-2-Version-3.jpg\/v4-728px-Find-the-Reciprocal-Step-2-Version-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
2
整数的倒数是分数。刚才说过,一个数的倒数就是1÷ (这个数)。[2]
整数可以直接写成分数形式,没必要通过计算把它变成分数。
方法 2 的 3:
求带分数的倒数
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/4\/42\/Find-the-Reciprocal-Step-3-Version-3.jpg\/v4-460px-Find-the-Reciprocal-Step-3-Version-3.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/4\/42\/Find-the-Reciprocal-Step-3-Version-3.jpg\/v4-728px-Find-the-Reciprocal-Step-3-Version-3.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
1
辨别哪些数是带分数。带分数一部分为整数,一部分为分数,比如 24/5。[3]
求带分数倒数的方法有两步,下面将详细说明。
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/5\/55\/Find-the-Reciprocal-Step-4-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-4-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/5\/55\/Find-the-Reciprocal-Step-4-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-4-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
2
把带分数变成假分数。记住,1可以写成 (数字)/(同一个数字),分母(分数线下面的数字)相同的分数可以直接相加。下面以 24/5举例说明:
- 24/5
- = 1 + 1 + 4/5
- = 5/5 + 5/5 + 4/5
- = (5+5+4)/5
- = 14/5.
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/7\/7e\/Find-the-Reciprocal-Step-5-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-5-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/7\/7e\/Find-the-Reciprocal-Step-5-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-5-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
3
把该分数上下颠倒。当带分数完全变成分数后,像处理其它分数一样将其上下颠倒,得到的就是它的倒数了。[4]
方法 3 的 3:
求小数的倒数
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/7\/72\/Find-the-Reciprocal-Step-6-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-6-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/7\/72\/Find-the-Reciprocal-Step-6-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-6-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
1
可能的话,将小数变成分数。有些常见的小数很容易转换为分数。[5]
比如,0.5 = 1/2,0.25 = 1/4。一旦小数变成分数,只要把分子分母上下颠倒就能得到它的倒数了。
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/d\/de\/Find-the-Reciprocal-Step-7-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-7-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/d\/de\/Find-the-Reciprocal-Step-7-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-7-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
2
用除法求倒数。如果你无法将小数变成分数,就用1 ÷ (这个小数)的方法算出它的倒数。你可以使用计算机,或者继续下个步骤心算出答案。[6]
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/d\/d9\/Find-the-Reciprocal-Step-8-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-8-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/d\/d9\/Find-the-Reciprocal-Step-8-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-8-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
3
将除法中的小数变成整数。小数除法的第一步是除去小数点,让除数和被除数都变成整数。只要将所有数字的小数点移动相同的位数就能得到正确的答案。
- 比如,你可以把1 ÷ 0.4写成10 ÷ 4。这里,你将每个数的小数点向右移动了一位,也就是将每个数乘以10。
-
{"smallUrl":"https:\/\/www.zenmeban.com\/images_en\/thumb\/5\/54\/Find-the-Reciprocal-Step-9-Version-2.jpg\/v4-460px-Find-the-Reciprocal-Step-9-Version-2.jpg","bigUrl":"https:\/\/www.zenmeban.com\/images\/thumb\/5\/54\/Find-the-Reciprocal-Step-9-Version-2.jpg\/v4-728px-Find-the-Reciprocal-Step-9-Version-2.jpg","smallWidth":460,"smallHeight":345,"bigWidth":728,"bigHeight":546,"licensing":"<div class=\"mw-parser-output\"><\/div>"}
4
用长除法求倒数。用[[做长除法|长除法]算出倒数。计算10 ÷ 4得到答案2.5,也就是0.4的倒数。
小提示
- 一个数的负倒数就是它的正倒数乘以负1。[7]
比如,3/4 的负倒数就是 -4/3。
- 倒数有时又叫作"乘法逆元素"。
- 1的倒数就是它自己,因为1 ÷ 1 = 1。
- 0没有倒数,因为1 ÷ 0没有意义。[8]