First, we need to convert 253 lb to kilograms. Given that 1 kg is equivalent to 2.205 lb, then:
The dosage Justin should receive is directly proportional to his weight. Given that a dosage of 11 mg corresponds to a weight of 20 kg, then to find the dosage that corresponds to 114.74 kg we can use the next proportion:
Solving for x:
He should receive a dosage of 63.1 mg