This trick here is to recognize that this is a real world question, and that the number of smokers must be an INTEGER.
For example, we can't have 17.4 female smokers.

GIVEN: 49% of the females smoke
If F = the total number of female workers, then the number of female SMOKERS = 49% of F = (49/100)F
This tells us that F must be a multiple of 100, otherwise, the number of female SMOKERS will not be an INTEGER
For example, 49% of 100 = 49, 49% of 200 = 98, 49% of 300 = 147, etc
Conversely, 49% of 50 = 24.5, 49% of 75 = 36.75, 49% of 60 = 29.4. etc

Since there are 200 workers in TOTAL, the number of females must be either 100 or 200
However, since we're told that 10% of the males smoke, we know that there must be at least 10 male workers.
So, there can't be 200 female workers, which means there must be 100 female workers.

We now know that there are 100 female workers and 100 male workers.
49% of 100 = 49, so there are 49 female SMOKERS
10% of 100 = 10, so there are 10 male SMOKERS
TOTAL number of SMOKERS = 49 + 10 = 59

Answer: C

Cheers,
Brent