It is possible that the student made a rounding error.

• Students should always enter exact answers unless an item specifies rounding. If the item does say to round, then the student is expected to round as directed. This is generally consistent with the Big Ideas Math Examples.
• Students should not round in intermediate steps. Rounding intermediate steps is contrary to the Mathematical Practice "Attend to precision," and the Big Ideas Math textbook Examples are generally solved without rounding until the final step. Following this pattern, we expect students to round only their final answer (when the item specifies rounding).