求问一道难题册的数学

沃卜植稻

Merle’s spare change jar has exactly 16 U.S. coins, each of which is a 1-cent coin, a 5-cent coin, a 10-cent coin, a 25-cent coin, or a 50-cent coin. If the total value of the coins in the jar is 288 U.S. cents, how many 1-cent coins are in the jar?

• The exact numbers of 10-cent, 25-cent, and 50-cent coins among the 16 coins in the jar are, respectively, 6, 5, and 2.
  
• Among the 16 coins in the jar there are twice as many 10-cent coins as 1-cent coins.
  
  答案是D， 1和2任意都可以推出，想问下条件2怎么单独推出呀
  
  

750嫁给我吧

一共16个硬币，288分
除了1分之外的硬币，无论各自多少，相加后只能是0或5结尾
推出1分要么3、要么8...
而10分又是1分的两倍，那1分只能是3

沃卜植稻

750嫁给我吧 发表于 2020-1-4 15:09
一共16个硬币，288分
除了1分之外的硬币，无论各自多少，相加后只能是0或5结尾
推出1分要么3、要么8...

哇谢谢！！