the doctor orders 20 mg of dermol. on hand are 5mg tablets, how many tablet will be given for a day period

Answer 1

20 mg x 1 tablet / 5 mg = 4 tablets. This is using dimensional analysis.

Looking at it another way: If you take 1 tablet, that's 5 mg. Two tablets will be 10 mg. Three tablets will be 15 mg and four tablets will be 20 mg.