Answer:
140 g
Explanation:
Note that
As you can see 5 is the common factor for all three numbers and 2 is the common factor only for the first two numbers. So, the greatest common factor

The smallest mass of the block should be 140 g (it can be cut into 14 pieces of 10 g weight, 7 pieces of 20 g weight or 4 pieces of 35 g weight).