Final answer:
The nurse will need to use 200 mL of the formula to make the 2/3 strength.
Step-by-step explanation:
To find the amount of 2/3 strength formula, you first need to determine how many mL of the formula will be used. The given information is that the nurse is preparing to administer 300mL of 2/3 strength formula. Since 2/3 is the strength of the formula, it means that 2/3 of the total volume is the formula itself. Therefore, to find the amount of formula, you can multiply the total volume by 2/3:
300 mL x 2/3 = 200 mL
So, the nurse will need to use 200 mL of the formula to make the 2/3 strength.