分数问题乍一眼看起来棘手,但是随着你的练习和诀窍的掌握,它们就会变得比较容易。下面就教你如何解答分数问题。
步骤
方法 1 的 4:
分数乘法
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1
确保你是在乘两个分数。 这些方法只在两个分数相乘时有效。如果有任何一个数字是带分数,首先一定要把它转化成假分数。
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2
分子乘以分子,分母乘以分母。
例如1/2 x 3/4,那就1 x3,2 x 4,得到的结果就是3/8。
方法 2 的 4:
分数除法
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1
确保你是在除两个分数。 再强调一次,这些方法只在你已经把所有的带分数转化成假分数的前提下有效!
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2
将第二个分数上下颠倒。 你应该能弄清这个“第二个”所指的是哪个分数。
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3
把除号改为乘号。
如果开始是8/15÷3/4,那么现在将它改为8/15 x 4/3。
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4
分子乘以分子,分母乘以分母。
8 x 4 得到 32 ,15 x 3 得到 45, 所以最终得出的结果是 32/45。
方法 3 的 4:
带分数转换成假分数
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1
把带分数转换成假分数。 假分数的分子大于分母。(比如17/5).当你在做乘法和除法时,你必须把带分数转换成假分数之后,再做进一步的运算。
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2
把整数部分与分母相乘。
在我们的例子中,3 x 5,即15。
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3
将相乘的结果与分子相加。
在我们的例子中,15+2,即17。
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4
把你所得到的数字作为分子放在原来的分母上,你会得出一个假分数。 (在我们的例子中,我们得到17/5)
方法 4 的 4:
分数加减
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1
找到最小公分母(底部数字),不管是分数的加法还是减法,你都得经过这个过程。 约分成最简分数,以便之后转换最小公分母进行运算。
举个例子,如果你遇到的数字是1/4和1/6,那么它们的最小公约数是12.(4x3=12, 6x2=12)
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2
分数乘法时一定要找最小公分母。 记住,当你这样做时并没有改变分数的数额,而只是改变了它的表达方式,分数的本质并没有变。想象一下比萨饼,1/2个比萨饼跟2/4个比萨饼是同样的数量。(4x3=12, 6x2=12)
找出当前的分母要扩大多少倍才能得到最小公分母 。例如1/4,4乘3得12;1/6,6乘2得12(所以1/4和1/6的最小公分母是12)。
同时把分母和分子与那个数相乘 。例如1/4,把1和4分别同3相乘,得到3/12.1/6上下同时乘2,得到2/12.现在你要解决的问题就是3/12 + 2/12或3/12 - 2/12。
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3
把这两个数的分子相加减(注意不是分母)。 这其中的奥妙在于你是想得到总共有多少个这种类型的分数。如果你同时也把分母加减了,你就会改变分数的类型。
例如3/12 + 2/12,你最终的答案是5/12。而对于3/12 - 2/12,结果就是1/12。
小提示
掌握四项基本的运算方法(乘法、除法、加法、减法),将有助于你轻松、快速掌握这个环节。
在做乘除的时候,你可以不用第一时间将带分数转化成假分数。但是这样做可能会导致更复杂地使用分配率。所以通常还是最好首先将带分数转化成假分数。
要想得到整数的倒数,只要把1放在整数头上就可以了。例如,5的倒数就变成了1/5.
“把分数颠倒“的另一个说法就是”求这个分数的倒数“。你只需要将分子和分母上下对换。例如,2/4的倒数得到4/2.
当你求一个负数的倒数时,负号停留在分子。
警告
在运算之前将带分数转化成假分数
和你的老师核对是否需要将运算结果约到最简分数。
和你的老师核对是否需要把假分数化成带分数。