To solve this problem, we can use a proportion since the amount of cheese is directly proportional to the number of pizzas.

The ratio of the number of pizzas to the amount of cheese is:

$\frac{4 \text{ pizzas}}{10 \text{ ounces of cheese}} = \frac{15 \text{ pizzas}}{x \text{ ounces of cheese}}$

Now we can cross-multiply to solve for $x$:

$4 \cdot x = 10 \cdot 15$

$4x = 150$

Now, divide both sides by 4:

$x = \frac{150}{4} = 37.5 \text{ ounces}$

So, Mai will need 37.5 ounces of cheese to make 15 pizzas.

Would you like more details or have any questions?

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Here are 5 related questions:

1. How much cheese would Mai need for 20 pizzas at this rate?
2. If Mai had only 25 ounces of cheese, how many pizzas could she make?
3. How many ounces of cheese would Mai need for 1 pizza?
4. What is the rate of cheese per pizza?
5. How many pizzas can be made with 50 ounces of cheese?

Tip: Proportions are a powerful way to solve problems involving scaling quantities!