Karan is five times as efficient as Varun and twice as

Solution

Since, Karan is five times as efficient as Varun, he will take one-fifth the time taken by Varun to finish the work. So, time taken by Karan to do the work = 30 ÷ 5 = 6 days And, Karan is twice as efficient as Arjun, so Arjun will take double the time taken by Karan. So, time taken by Arjun to do the work = 2 × 6 = 12 days Let the total work be '12x' units. So, efficiency of Karan = 12x ÷ 6 = '2x' units/day And, efficiency of Arjun = 12x ÷ 12 = 'x' units/day So, required time = 12x ÷ (2x + x) = 4 days Hence, option c.