## 20120909

### Physics quiz question: subtracting distance measurements

Physics 205A Quiz 1, fall semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 1.57

Evaluate the following calculation, using an appropriate number of significant figures and/or decimal places.

5.99 in – 0.99 in = ?

(A) 5 in.
(B) 5.0 in.
(C) 5.00 in.
(D) 5.000 in.

Correct answer (highlight to unhide): (C)

While 5.99 in has three significant figures (shown in green), and 0.99 inches has two significant figures, both 5.99 in and 0.99 in have two decimal places (shown in gray).

For addition and subtraction operations, the term with the least number of decimal places determines the number of significant decimal places in the result:

5.99 in – 0.99 in = 5.00 in.

Thus the result of this subtraction must also have two decimal places.

Sections 70854, 70855
Exam code: quiz01bL0t
(A) : 2 students
(B) : 9 students
(C) : 50 students
(D) : 0 students

Success level: 82%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60