Some persons can do a piece of work in 12 days. Two times the number of such…
2024
Some persons can do a piece of work in 12 days. Two times the number of such persons will do half of that work in:
- A.
6 days
- B.
12 days
- C.
4 days
- D.
3 days
Attempted by 108 students.
Show answer & explanation
Correct answer: D
Solution: Let the number of persons be n.
Step 1: Total work = number of persons × time = n × 12 = 12n person-days.
Step 2: Half of that work = (1/2) × 12n = 6n person-days.
Step 3: Number of workers now = 2n, so time = work ÷ workers = 6n ÷ 2n = 3 days.
Answer: 3 days.
Common mistake: Confusing time for the full work with time for half the work. Doubling workers halves the time for the full job (from 12 to 6 days), and half the job then takes half of that time (3 days).