一石二鸟
Meaning
To achieve two goals with a single action — the Chinese equivalent of "kill two birds with one stone".
In a sentence
Walking to work is 一石二鸟: exercise and no traffic.
Usage note
Neutral and common in planning contexts.
Where you see it in Brain Challenge
This idiom appears in the picture-idiom levels as a picture or number clue. When the clue shows numbers, the digits usually become the first characters of each half of the idiom — that is why so many chengyu start with 一, 三, 五, 七, 九 or 十.