The farmer

The farmer calculated that the supply of fodder for his 20 cows was enough for 60 days. He decided to sell two cows and a third of the feed. How long will feed the rest of the peasant's herd last?

Correct answer:

t =  44.4444 d

Step-by-step explanation:

$$\begin{gathered} n=20 \\ d=60 \\ n\cdot d-n\cdot d/3=t\cdot (n-2) \\ 20\cdot 60-20\cdot 60/3=t\cdot (20-2) \\ 54t=2400 \\ t=\frac{2400}{54}=44.44444444 \\ t=\frac{400}{9}\doteq 44.444444=44.4444\text{d} \end{gathered}$$

Try another example