"a 20 dollar bill”中dollar为什么不用复数?

"a 20 dollar bill”中dollar为什么不用复数? That's a 15 dollar fine.这句话里dollar为什么不用复数形式dollars? 为什么"the 20 dollar"的"dollar"后面不用加"s"? million dollar bill DOLLAR a 20 dollar fine翻译 He gave the taxi driver a—.A five dollar bill B five--dollar dollar的复数是什么 dollar 复数是什么? A dollar ten=$1.10 为什么? a dollar for Haiti Chase graced the 10,000 dollar bill