Please answer the following question by reasoning step-by-step.
Ruel has four books of 10 stamps and six books of 15 stamps. How many stamps does Ruel have?

130
Ruel has a total of 4 x 10 = 40 stamps from the four books.

He also has 6 x 15 = 90 stamps from the six books.

Therefore, he has a total of 40 + 90 = 130 stamps.

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The answer is 130