In order for the scales to balance the block on the right side must be 10 kg.
It is possible to use the same weights to weigh, for example, 4 kg.
In fact using 2 kg, 3 kg and 5 kg weights it is possible to weigh all but one value from 1 kg to 10 kg. What is that value?
(Note: You don't have to use all three weights.)