事半功倍 achieve twice the result with half the effort
Explanation
事半功倍，指做事的方法对头，费力少，效率高，效果好。
It means that with the right method, one can achieve high efficiency and good results with little effort.
Origin Story
战国时期，齐国有个叫田忌的人，善于赛马。一次，他和齐威王赛马，约定三局两胜。田忌的三匹马，分别是一匹上等马，一匹中等马和一匹下等马；而齐威王的三匹马也分别是一匹上等马，一匹中等马和一匹下等马。按常理，田忌肯定输。但田忌运用计策，用自己的上等马对齐威王的中等马，用自己的中等马对齐威王的下等马，用自己的下等马对齐威王的 上等马。结果，田忌赢了两局，大胜齐威王。这是因为田忌掌握了制胜的法则，用巧妙的策略，达到了事半功倍的效果。
During the Warring States period in China, there was a man named Tian Ji who was skilled in horse racing. Once, he competed with King Qi Wei in a horse race, agreeing on three rounds, with two wins securing the overall victory. Tian Ji's three horses consisted of a superior horse, a middle-class horse, and an inferior horse; King Qi Wei's three horses also consisted of a superior horse, a middle-class horse, and an inferior horse. Normally, Tian Ji would have lost. But Tian Ji used a strategy, pitting his superior horse against the King's middle-class horse, his middle-class horse against the King's inferior horse, and his inferior horse against the King's superior horse. As a result, Tian Ji won two rounds and defeated King Qi Wei. This was because Tian Ji mastered the rules of victory and, with clever strategies, achieved maximum results with minimal effort.
Usage
常用来形容做事方法好，效率高。
It is often used to describe a good method and high efficiency.
Examples
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只要方法得当，就能事半功倍。
zhǐyào fāngfǎ dédàng, jiù néng shì bàn gōng bèi
As long as the method is appropriate, we can achieve twice the result with half the effort.
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这次的改革措施，使我们的工作事半功倍。
zhè cì de gǎigé cuòshī, shǐ wǒmen de gōngzuò shì bàn gōng bèi
This reform measure has enabled us to achieve twice the result with half the effort in our work.