What is a normal dosage of amoxicillin for a 3 yr old child weighing 28 lbs?

40 mg/ pound. The dosage can vary but Amoxicillin is very safe at low and high doses. The general dose is 40 to 80 mg per kilo, usually divided 2 times per day.
Depends on illness. It really depends on the illness. For severe infections high dose Amoxicillin may be warranted whereas low dose Amoxicillin may be prescribed for local skin infection. Talk to you doctor if you are questioning the dose given to your child.
Varies. Dosages of Amoxicillin are different depending on the illness to treat. For instance , much higher dose of Amoxicillin is prescribed for ear infection than for strep throat.