GMAT数学算数知识精解_GMAT数学

GMAT数学算数知识精解

　　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 is　a

　　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。

　　八.描述统计平均数

　　2.中数

　　To calculate the median of n numbers，first order the numbers from least to greatest;if n is odd，the median is defined as the middle number，while if n is even，the median is defined as the average of the two middle numbers. For the data 6, 4, 7, 10, 4, the numbers, in order, are 4, 4, 6, 7, 10, and the median is 6, the middle number. For the numbers 4, 6, 6, 8, 9, 12, the median is /2 = 7. Note that the mean of these numbers is 7.5.