英语倍数问题真晕The volume of trade between the two countries,as is

三倍:
1.triple
其它相关解释:
例句与用法:
1.我丈夫挣的钱是我的三倍.
My husband earns thrice the amount I earn.
2.我们公司的利润在这两年中增加了三倍.
Profits in our company have trebled in the last two years.
3.产量已增加到三倍.
Output has tripled.
4.三倍,三重是三倍或三重的性质或状态
The quality or condition of being triple.
5.去年以来该报的发行量已增加到原来的三倍.
The newspaper's circulation has trebled since last year.
thrice:[ θrais ]
ad.三倍地,三次
例句与用法:
1.My husband earns thrice the amount I earn.
我丈夫挣的钱是我的三倍.
2.He flung off his opponent thrice.
他把对手摔倒三次.
副词thrice:
1.three times
treble:[ 'trebl ]
n.最高音部
a.三倍的,最高部的
v.使...增为三倍
词形变化:
副词:trebly 名词:trebleness 动词过去式:trebled 过去分词:trebled 现在分词:trebling 第三人称单数:trebles
例句与用法:
1.Profits in our company have trebled in the last two years.
我们公司的利润在这两年中增加了三倍.
2.He sings treble.
他唱最高音部.
名词treble:
1.the pitch range of the highest female voice
同义词：soprano
动词treble:
1.sing treble
2.increase threefold
同义词：triple
形容词treble:
1.having or denoting a high range
同义词：soprano
2.three times as great or many
同义词：threefold,three-fold,triple
3.having three units or components or elements
同义词：ternary,triple,triplex
4.having more than one decidedly dissimilar aspects or qualities-Frederick Harrison
同义词：double,dual,twofold,two-fold,threefold,three-fold

增加到4倍.......

fourfold 是 原量乘四的意思， 也就是增长了三倍，是原来的四倍的意思
has doubled 就是翻倍的意思，一样的

In some cases output has increased more than fourfold.
在有些情况下，产量增加了3倍多。
是增加到四倍
没错