The librarian was checking the thicknesses of several books and found that the average thickness of a book was 1.8 centimeters. She found this by averaging the thickness of five different books. Four of the thicknesses were 1.4cm, 1.9 cm, 2.1 cm, and 2.4 cm. What was the thickness of the fifth book that she measured?
These must be books for young children
5 * 1.8 = 9
1.4 + 1.9 + 2.1 * 2.4 + x = 9
Solve for x.
The librarian measured the thickness of the textbooks in the school library. Among a selection of 7 books, he recorded the following thicknesses:
To find the thickness of the fifth book, we can use the average thickness and the thicknesses of the other four books.
First, we add up the thicknesses of the four books: 1.4 cm + 1.9 cm + 2.1 cm + 2.4 cm = 7.8 cm.
Next, we calculate the sum of all five books by multiplying the average thickness by the total number of books, which is 5: Average thickness * Number of books = 1.8 cm * 5 = 9 cm.
Now, we can find the thickness of the fifth book by subtracting the sum of the other four books from the total sum: Total sum - Sum of four books = 9 cm - 7.8 cm = 1.2 cm.
Therefore, the thickness of the fifth book that the librarian measured is 1.2 centimeters.