I started by making the equation: a+b+c+d=40 because that would provide me with the largest value that we can make with the 4 weights. Then I decided that a<b<c<d. Then I walked down the list from the first equation.
Ex.
a+b+c+d=40
b+c+d=39
a=1
b+c+d=38+a
a+c+d=37
b=3
Ect.
After following this for a bit I found that a=1, b=3, c = 9, and d=27.
You set a clear start with a+b+c+d=40 and the ordering a< b <c<d but the steps that follow ... read as conclusions without the missing reasons. Where does the two-pan feature (being able to place weights on either side) enter your argument? What makes
ReplyDeletea=1 necessary rather than a=2? What eliminates b=2 and forces b=3 . What principle generates d and guarantees no gaps from 1 to 40? And how do you verify that 1,3,9,27 truly reaches every integer in that interval, not just 40?