(1) this topic examines the relationship between work efficiency, working hours and workload, and can be solved by finding out the workload and work efficiency corresponding to the required time;

(2) Multiply the original working efficiency by the working time to find out how many parts have been processed, and then find out the number of remaining parts, and divide the number of remaining parts by the later working efficiency, which is the required time.

explain

Solution:

Number of pieces processed = 100×20=2000 (pieces)

Number of remaining parts =2480-2000=480 (pieces)

Time required to process the remaining parts =480÷ 120=4 (days) A: It will take another 4 days to complete the task.