Final answer:
To find the number of capsules needed, divide the total amount of ampicillin required by the amount of ampicillin in each capsule. In this case, the child should be given 4 capsules.
Step-by-step explanation:
To find the number of capsules that should be given, we need to calculate the total amount of ampicillin required and then divide it by the amount of ampicillin in each capsule.
The recommended dose of ampicillin is 45 mg/kg, and the child's mass is 22 kg. So, the total amount of ampicillin required is 45 mg/kg x 22 kg = 990 mg.
Each capsule contains 250 mg of ampicillin. Therefore, the number of capsules needed is 990 mg / 250 mg per capsule = 3.96 capsules.
Since we cannot give a fraction of a capsule, we round it up to the nearest whole number. Hence, the child should be given 4 capsules of ampicillin.