Scale puzzle

I misunderstood the question so I got the bellow mentioned the solution. 

A market vendor sells dried cooking herbs in whole-number amounts from 1 to 40 grams. The vendor has an old-fashioned two pan weigh scale, and has exactly four weights of different amounts that allows them to weigh out any of these amounts of herbs -- without using the herbs or any other object as an auxiliary weight.

What are the values of the four weights?

The values of the four weights are 1, 2, 3, and 5 grams. Those all are prime numbers.

Are there several correct solutions?

Yes, there are various correct solutions. For example, we can use other prime numbers which also come from 1 to 40. Like 7, 11, 13, up to 40. However, we have 7 if we add 2 and 5 and we have 11 if we add 5+5+1. I have noticed that I can use the smallest first four prime numbers. Therefore, the values of the four weights are 1, 2, 3, and 5 grams.

I have revised my solution. 
My current solution is have mentioned below:

The values of the four weights are 1, 3, 9, and 27 grams. there is no various solution we have for the puzzle.

1 and 3 gave the most consecutive numbers starting at 1. 9 would be the next number to add in order to get the number 13 - 5. 5 = 9-3-1 and so on. 1+3+9+27=40.

How could you extend this puzzle to help your students understand the mathematics more deeply?

I can extend this puzzle in various ways that help my students understand math more deeply. I can give a bigger number rather than 40 or restrict them to use only odd/even numbers to use for the value of weight.  I ask them open-ended questions: What if we do not use prime numbers for the values of the weight?