you didn't include how many gallons each container of bleach has, so I'm just going assume one container has a gallon inside. if 5% of one gallon is active Ingredients, and there are 10 gallons, then that's 1,000%. (one gal = 100%. 100x10= 1,000) 5 x 10= 50, so 50% of 1,000% is active ingredients, which can be simplified to 5% anyway, so 5%