Hens $=$ baby chickens $\times\dfrac{8}{9}$,  Roosters $=$ hens $\times\dfrac{1}{16}$,  We can write the formula as:~$3600\times\dfrac{8}{9}\times\dfrac{1}{16}=3200\times\dfrac{1}{16}=200$. 
There are $3600$ baby chickens on a farm. The number of hens on the farm is $\dfrac{8}{9}$~of the baby chickens, and the number of roosters is $\dfrac{1}{16}$~of the number of hens. How many roosters are there on the farm? 

1) $$180$$ 
2) $$200$$ 
3) $$100$$ 
4) $$225$$ 