Let's denote the total work as W.
Amal and Vimal together can-do W work in 150 days, so their combined efficiency is W/150. Vimal and Sunil together can-do W work in 100 days, so their combined efficiency is W/100.
Let A, B, and C be the individual efficiencies of Amal, Vimal, and Sunil, respectively. From the given information, we can form the following equations:
1. A + B = \(\frac{W}{150}\)
2. B + C = \(\frac{W}{100}\)
Now, let's analyze the second scenario where they work on alternate days: Amal works on all days, so his work in one day is A. Vimal works on every second day, so his work in two days is B. Sunil works on every third day, so his work in three days is C.
So, in 6 days, they complete A + B + C work.
To find the total number of days required, we need to find how many times 6 divides the total work W. We can calculate this by dividing W by the work done in 6 days:
Total days = \(\frac{W}{A + B + C}\)
We can solve the equations for A, B, and C and substitute them into the above equation to find the total number of days.
After solving, we get the total number of days as 139.