what will be the minimum pressure required to compress 500dm³ of air at 1bar to 200 dm³at 30 degree celsius ?

As we know from Boyle's Law,
          P₁V₁ = P₂V₂
Given,
          Initial Pressure, P₁  = 1 bar
          Initial Volume, V₁  = 500 dm³
          Final Volume, V₂   = 200 dm³
          Final Pressure, P₂   = ?

From boyle's law

           P₁V₁ = P₂V₂
Substituting the values, we get,
            
           P₂ =  P₁V₁ / V₂
                =  (1 x 500) / 200
                =  2.5 bar