To solve this problem, we can set up a proportion to find the amount of sunscreen Yoku needs to cover 325 cm² of his skin.
We know that it takes 2 ml of sunscreen to cover 50 cm² of his skin. Let's set up the proportion:
2 ml / 50 cm² = x ml / 325 cm²
To solve for x (the amount of sunscreen needed to cover 325 cm²), we can cross-multiply and solve for x.
(2 ml) * (325 cm²) = (50 cm²) * x ml
650 ml * cm² = 50x ml * cm²
Now we can cancel out the cm² units:
650 ml = 50x ml
To isolate x and solve for the amount of sunscreen needed, divide both sides by 50:
650 ml / 50 = x ml
x = 13 ml
Therefore, Yoku will need 13 ml of sunscreen to cover 325 cm² of his skin.