Math repost for Andy
posted by Writeacher on .
math  Andy, Thursday, October 25, 2007 at 7:37pm
can you please help me with this math problem? If you can here is the question:
Seventyfive years ago, pharmacists weighed medicine on balances like the ones you have been using. The mass pieces were very expensive, so a pharmacist would buy as few mass pieces as possible. If a pharmacist had 1g, 3g, and 9g mass pieces, he or she could weigh out any number of grams from 1g to 13g. Show how you could measure all of the masses from ig to 13g using only the three mass pieces given

for 1 g, use the 1g piece on one side top balance the material bing measured.
For 2 g, put 3g on one side and 1 on the other. Add material to the side with the 1 g mass.
For 3 g, use the 3g piece to balance.
For 4 g, put the 1 g and 3 g together on one side
For 5 g, Put 9 g on one side and 3 + 1 on the other
Similarly, 6 = 9  3
7 = 9 + 1  3
8 = 9  1
9 = 9
10 = 9 + 1
11 = 9 + 3  1
12= 9 + 3
13 = 9+3+1 (all on the same side)