I am stuck at how to work out how I make 500mls of a stock solution. I had a question about making initially 500ml of sodium chloride 0.9% for 500ml. I think I am correct in thinking that I needed 4.5gms.

From this, I need to make another 500ml of 0.45%.

Do I need to multiply 0.45 by 500? I think I need to divide this answer by another figure but I can't remember which one! As you guys can see, maths is a sore point for me.

From this, I need to make another 500ml of 0.45%.

Do I need to multiply 0.45 by 500? I think I need to divide this answer by another figure but I can't remember which one! As you guys can see, maths is a sore point for me.

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