Use divisibility rules to find the way through a number maze

This is a puzzle that works well with calculators. They can be frustrating at first due to the many possible paths, but they are actually not very hard if divisibility rules are used. For example, if the product at the end is a multiple of 7 and there is only one 7 on the board, then the path must pass through that cell. Counting up even and odd numbers of negative values also helps. Even the largest board can be solved by fully factorizing the product.

Each puzzle has only one path that leads to the correct result.