Article From:https://www.cnblogs.com/chiweiming/p/9124325.html

Original

Title: change the zero note

xThe denomination of the money on the planet is only 100 yuan, 5 yuan, 2 yuan, 1 yuan, 4 kinds.
Xiaoming went to x star travel. He only had 2 100 yuan x star coins in his hand, which was too inconvenient. He just went through the X Star Bank to change the money.
Xiao Ming has a bit of obsessive compulsive disorder. He insisted on asking for 200 yuan to change the number of Zhang Zhang in 2 yuan, which is 10 times the number of 1 yuan.
The rest of course, of course, is 5 yuan.
The staff of the bank are in a bit of a dilemma. Can you help figure out how many bills should be changed to meet the requirements of Xiaoming?
（5Yuan, 2 yuan, 1 yuan denomination must have, can not be 0.

Note that you need to submit an integer and do not fill in any unnecessary content.

Solved by mathematical method:

The minimum number of notes required is 5 yuan bills.

Set 1 yuan notes with X Zhang, then 2 yuan notes have 10x Zhang, 5 yuan notes y Zhang.

There are: x+2*10x+5y=200

Collate: y=40-21*x/5

To think of the largest y, X must be the smallest, so x=5;

So1 There are 5 yuan bills, but there are 50 yuan in 2 yuan bills and 19 in 5 yuan bills.