I took a different approach, which helped me solve it orally.
Let 1 man work 4 units/day. (I took 4 units because half and quarter would be simpler when we solve the question further. You can take any number)
That makes 4 men work 16units/day.
Total units = 11*16 = 176 units to be completed.
Earlier, 4 men were working 16units/day and that’s how they completed in 11 days.
Now, 2 men are working at usual 4units/day. 3rd man is working at 2units/day and 4th man is working at 1 unit/day.
Total units of work done in 1 day is 4+4+2+1 = 11.
Total work to be done 176 units.
176/11 = 16 days.