For example, a highway is planned to be built 200 meters a day for 24 days. I actually built 480 meters in two days. How many days did it actually take? Answer in direct proportion. The work efficiency is certain, and the workload is directly proportional to the working hours.

Assumption: actually completed in x days.

480: 2 = (200 * 24): x solution:

480:2=4800:X

480X=2×4800

480X=9600

X=20

Property: the product of external items is equal to the product of internal items!