Calculate the mass of h2o and c6 h12 o6 required to make 250 gram of 40% solution of glucose

40% solution of glucose is where the solution contains, by weight, 40% glucose and 60% water. 

Therefore, if the total weight of the solution is 250 g, 
mass of the glucose (C6H12O6) = 250 g * 40% = 100 g
mass of water (H2O) = 250 g * 60% = 150 g

Mass of water can also be calculated by subtracting the weight of glucose from the total weight of the solution:
mass of water = 250g-100g = 150g.