'Zara' is capable of finishing a specific task in 60

Solution

ATQ,   Time taken by ‘Armaan’ alone to complete the whole task= 1.40 × 60 = 84 days   Time taken by ‘Tara’ alone to complete the whole task = 1.75 × 60 = 105 days Total task = 420 units (LCM of 60, 84 and 105) Efficiency of ‘Armaan’ = 420/84 = 5 units per day   Efficiency of ‘Tara’ = 420/105 = 4 units per day   Efficiency of ‘Zara’ = 420/60 = 7 units per day Task completed by ‘Armaan’, ‘Tara’ and ‘Zara’ together in 3 days = 5 + 5 + 16 = 26 units   Task done by Armaan, Tara and Zara together in 48 days = 16 × 26 = 416 units  Remaining 4 units Task will be completed by Armaan alone in 4/5 days  Hence required time = 48 + (4/5) = 48.8 days or 49 days