Use a product rule of exponents to simplify 5 to the 10th power times 5 to the 5th power? Would answer be 5 to the 15th power?

Yes, you are correct. Using the product rule of exponents, when you multiply two numbers with the same base, you add their exponents. Therefore, 5 to the 10th power times 5 to the 5th power is equal to 5 to the (10 + 5)th power, which simplifies to 5 to the 15th power.