A person can complete a job in 120 days. He works alone on Day 1. On Day 2, he is joined by another person who also can complete the job in exactly 120 days. On Day 3, they are joined by another person of equal efficiency. Like this, everyday a new person with the same efficiency joins the work. How many days are required to complete the job?
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This one looked so easy until I realized the work per day keeps changing. Classic trap!
Same, I almost just did 120/2 and moved on 😅
Yup, the increasing workforce is the whole trick here.
Is there a quick way to set this up without listing every day? The sum 1+2+3+... keeps growing and I got lost around day 10.
Think about the pattern of total work done after n days, it clicks fast.
Got B and it felt clean once I saw the symmetry. 605-655 feels right for this.
Nice, took me longer than it should have but same answer.
The fact that everyone works at exactly the same rate makes it way more manageable than the wording suggests.
What it tests
Your ability to combine individual work rates, usually by working with the fraction of a job completed per unit of time.
Common trap
Adding the times instead of the rates, or forgetting to take the reciprocal when combining rates.