common balance and weights?

Question

There are 3 identical sets of 5 weights each.....Using these weights and a common balance one can measure any integral weight (in gm) from1 gm to N gm.

whats the the maximum possible value of N ?

1)1023
2)363
3)8403
4)4647

whats the quick answer ?

Answer 1

8403. By "common" I assume you mean 2 pans, not pan and beam. Then each set contains 1, 7, 49, 343 and 2401 g weights for a total of 8403.
Derived by:
Gotta have 1g. This means you can directly weigh up to 3g, and by putting those weights on the same pan as the sample to be weighed, you can weigh a 4g sample with a 7g weight on the other pan. Then we can weigh 3*(1*7) = 24g directly, and can weigh 25g with 24g+25g sample vs. 49g. And so on.

Answer 2

answer is 32767. The formual is (2^n)-1
In this cas, the answer is (2^15)-1 = 32767.