九牛一毛
Meaning
A tiny, negligible fraction of something large — a drop in the ocean.
In a sentence
The repair cost is 九牛一毛 compared with the price of the car.
Usage note
Used to minimise an amount by contrast, not to insult.
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.