There are 4 wrenches just unpacked from a box. They all look the same. There might be one defective item which is either heavier or lighter. Fortunately there is a fifth one that is standard. If you can use a scale to weigh only 2 times, can you find out:
- Is there a defective wrench?
- If there is a defective item, is it heavier or lighter?
(In reply to re(2): Balanced solution
In that case, your solution seems to be okay for both the questions.