Max has $125 consisting of bills each worth either $5 or $20.
How many bills worth $5 does Max have? (1) Max has fewer than 5
bills worth $5 each. (2) Max has more than 5 bills worth $20
each. 125 = 5x + 20y x = ? the units digit of 125 is 5. From the
equation 20y will always yield a value with 0 as it's units
digit. While 5x will then have to yield a value that ends with
5. (1) if x is less than 5 then, we can choose from 0,1,2,3,4
but 5x should end with 5 so, we are left with 1 and 3 as
possibilities. Let x=1, the 20y should be 120, y=6 let x=3, then
5x=15 so 20y should be 125-15=110. But 110 is not a multiple of
20 so, not possible. Thus, x=1. SUFFICIENT (2) if y is greater
than 5 Let us try y=6, this is possible! Let us try y=7, 20y =
140, this is not possible or our eq. thus, y=6. SUFFICIENT