Give the step-by-step reasoning process and then the final answer. Danny brings 3 watermelons to his family picnic. He cuts each watermelon into 10 slices. His sister brings 1 watermelon to the family picnic, and she cuts the watermelon into 15 slices. How many watermelon slices are there in total at the picnic?
From Danny, there are 3 * 10 = 30 watermelon slices. From his sister, there are 1 * 15 = 15 watermelon slices. There are a total of 30 + 15 = 45 watermelon slices.
The final answer: 45.