What is a real world problem that could be solved by using a proportion?

One real-world problem that can be solved using a proportion is determining the correct dosage of medication based on a patient's weight. For instance, if a medication is prescribed at a dosage of 10 mg per 20 kg of body weight, a doctor can use a proportion to calculate the appropriate dosage for a patient weighing 70 kg. By setting up the proportion (10 mg/20 kg = x mg/70 kg), the doctor can easily find the correct dosage, ensuring the patient receives the right amount of medication for their weight.