Question

the layer of gold coating on a ring should be 0.03 mm thick when the ring is completed. a coating of 0.021 mm has already been applied. how many more mm of gold coating must be added to finish the ring ?

Answer 1

0.009 mm

Explanation:

Find the difference between the two values.

0.03 - 0.021

0.009 mm more gold coating must be added to finish the ring.