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Panu, Jiban and Jalil complete a task alone in 30, 20 and 60 days respectively. Jiban works daily and Panu and Jalil help on every third day. How many days to finish?
A13
B12
C15
D14
Answer & Solution
Correct answer: C. 15
1. Daily rates: Jiban 1/20, Panu 1/30, Jalil 1/60.
2. Day 1 and Day 2 Jiban alone: 1/20 each. Day 3 all three: 1/20 + 1/30 + 1/60 = 6/60 = 1/10.
3. One 3-day cycle = 1/20 + 1/20 + 1/10 = 1/5. Five cycles = 5 x 1/5 = 1 (whole task), so 5 x 3 = 15 days.
_Source: RRB Group D CEN-02/2018 PYQ, Q.32._
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