Master Li has been producing a batch of parts for 16 days, with an average of 45 per day, so it will take 4 days to complete the task. How many parts are there in this batch?
李师傅生产一批零件，已经生产了16天，平均每天生产45个，这样还要4天才能完成任务，这批零件有多少个？
<gadget id="calculator">16 + 4</gadget>
<output>20</output>

<gadget id="calculator">45 * 20</gadget>
<output>900</output>

<result>900</result>