Question

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 thicknesses of five different books. Four of the thicknesses were 1.4 cm, 1.9 cm, 2.1 cm, and 2.4 cm. What was the thickness of the fifth book that she measured?

Answer 1

1.2 cm

Explanation:

1.8 * 5 = 9

9 - (1.4 + 1.9 + 2.1 + 2.4) = 1.2

1.2 + 1.4 + 1.9 + 2.1 + 2.4 = 9

9/5 = 1.8