Aakash and Bijoy can separately do a piece of work in 20 days and 15 days, respectively. They worked together for 6 days, after which Bijoy was replaced by Chandrakant. If the work was finished in next 4 days, then for how many days did Chandrakant work?

Using the least common multiple method, let the total work be 60 units, so Aakash does 3 units daily and Bijoy does 4 units daily. In 6 days of working together, they complete 42 units, leaving 18 units for Chandrakant to finish over the next 4 days. By dividing the 18 remaining units by 4 days, Chandrakant's daily work is 4.5 units, meaning his individual capacity to complete the 60-unit job alone is 60 divided by 4.5, which equals 40 days.

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