I have mixed lead-tin alloys from 40-1 thru 20-1 for black powder & target smokeless loads..but for some reason, my brain can't seem to figure out how to do this: I have 10lb. of 40-1 lead-tin alloy. This is 2.5% tin/97.5% lead. How much tin must I add to equal a 30-1 lead/tin alloy of 3% tin/97%lead. I would like to have the math formula. Thank you!