Micaela and three of her friends volunteered to collect children's books for the city's homeless shelters. There are 4 homeless shelters in the area, and each shelter received 18 books. How many books did Micaela and her three friends collect altogether? (1 point)
• 27
• 72
• 18
• 4.5
If each shelter received 18 books, and there are 4 shelters in total, then the total number of books collected is 18 * 4 = <<18*4=72>>72 books.
Therefore, the correct answer is 72.