A chemical solution is 5% iodine. How many milliliters of iodine are there in 1,000 mL of

solution?

whatever% of anything is just (whatever/100) * anything.

in 1000mL of solution, there are of course 5% of iodine, how much is 5% of 1000? well is just (5/100) * 1000, or 50 mL.

50 milliliter since 5% of 1000 is 50 ml and there is only 5% iodine