GMAT数学--算术概述（二）

二.分数：fractions

分子：numerator

分母：denominator

分数的加减乘除：addition，subtraction，multiplication and division of fractions

繁分数和假分数：mixed number and improper fraction

繁分数是指一个数由一个整数和一个分数构成。

假分数是指分子大于分母的分数。例如：7/3

三.小数：decimals

科学计数法：scientific notation

Sometimes decimals are expressed as the product of a number with only one digit to the left of the decimal point and a power of 10. This is called scientific notation. For example, 231 can be written as 2.31×102 and 0.0231 can be written as 2.31×10-2. When a number is expressed in scientific notation, the exponent of the

10 indicates the number of places that the decimal point is to be moved in the number that is to be multiplied by a power of 10 in order to obtain the product. The decimal point is moved to the right if the exponent is positive and to the left if the exponent is negative. For example, 20.13×103 is equal to 20,130 and 1.91×10-4 is equal to 0.000191.

四舍五入：to the nearest

小数点：decimal point，period

四.实数：real numbers

正数和负数：positive and negative numbers

绝对值：absolute value

五.比率与比例：ratio and proportion

一个比率ratio可以表示成许多方式，例如：the ratio of 2 to 3可以被表达为2 to 3，2：3，或者2/3。注意比率中的中项的顺序是重要的，即2 to 3和3 to 2不同。A proportion isa

statement that two ratios are equal。例如：2/3=8/12是一个proportion。

六.百分比：percent

Percent means per hundred or number out of 100。

在考题中经常会问到从某一数量到另一数量百分比的增加或减少。首先算出增加或减少的量，然后除以原来的那个量，即“from”或“than”后面的量。

七.数的幂和根：powers and roots of numbers

x n意味着the nth power of x。例如：64 is the 6th power of 2。2 is a 6th root of 64。

立方根是指cube root。