J, K and L together can complete a book in 20 days. J and K together can complete the same book in 25 days. L alone can complete the same book in how many days?

Correct option is C

Given:
J, K, and L together can complete the book in 20 days, and J and K together can complete it in 25 days.
Concept Used:
The LCM method is used to calculate the total work and individual work rates.
Solution:
Let the total work be the LCM of 20 and 25, which is 100 units
Efficiency of J + K + L = 100 / 20 = 5 units per day.
Efficiency of J + K = 100 / 25 = 4 units per day.
Efficiency of L alone = Work rate of (J + K + L) - Work rate of (J + K)
Efficiency of L = 5 - 4 = 1 unit per day.
Therefore, L alone can complete the 100 units of work in:
Time taken by L = 100 / 1 = 100 days.