Sǐjì-yìngbèi xué yǔyán shì shìbèi-gōngbàn de zuòfǎ.
Learning a language by rote memorization is a case of twice the effort, half the result.
Tips
history
From 《孟子·公孙丑上》, where Mencius contrasts his era with the sages of old: half their effort would bring twice the result. 事倍功半 is the inverse - twice the effort, half the result.
mistakes
Do not confuse with 事半功倍 ('half the effort, twice the result') - the two idioms are exact opposites and swapping 倍/半 flips the meaning.
