Puzzle 9 : The 4 coins problem

 Solution to puzzle 8:

Maria is not counting Sundays. So she is not counting 1/7th of days of her age. 

That is to say she is only counting 6/7th of her age.

6/7th of her age = 30

Her actual age = 30 X 7/6 = 210/6 = 35 years. 

Puzzle 9 : The 4 coins problem

 You’re creating a new coin system for your country. You must use only four coin values and you must be able to create the values 1 through 10 using one coin at a minimum and two coins maximum. 

 

What 4 coins do you choose, and can you think of a second set of 4 coins that achieves the same goal?