Dividing 520 by 30 gives a quotient of 17 with a remainder of 10. In other words,  \[
520 = 30 \cdot 17 + 10.
\]Thus $30\cdot 17 = \boxed{510}$ is the largest multiple of 30 which is less than 520.
What is the largest multiple of 30 which is less than 520?
{'answer': '510', 'subject': 'Prealgebra', 'level': 1, 'unique_id': 'test/prealgebra/1829.json'}