35 students can finish working on the science lab project in 50 days. How many…

For a fixed piece of work done at a constant rate per worker, the number of workers and the number of days needed are inversely proportional -- their product, the total work measured in worker-days, stays constant no matter how the team size changes.

1. Find the total work for the project in student-days: multiply the original team size by the days it took them, 35 students times 50 days.

2. Since the total work stays the same, divide that student-days figure by the new team size of 20 students to get the number of days they need.

Check the result by multiplying the new team size by the computed number of days -- it should reproduce the same total student-days figure from step 1, confirming the total work has not changed.

So 20 students take 87.5 days to complete the same project.