Physics quiz question: mass of a letter-size page

Physics 205A Quiz 1, fall semester 2018
Cuesta College, San Luis Obispo, CA

"Standard bond" paper[*] has an area density of 75 g/m². A letter-size sheet of this paper has dimensions of 8.5 inches by 11 inches. A meter is defined to be 100 cm, and an inch is exactly equal to 2.54 cm. The mass of a single sheet of letter-size paper is:
(A) 0.28 g.
(B) 1.8 g.
(C) 4.5 g.
(D) 5.2 g.

[*] oki.com/us/printing/support/understanding-paper-weight/.

Correct answer (highlight to unhide): (C)

The mass of a single sheet of letter-size paper can be determined from converting the units from the given value of 75 g/m², by setting up conversion factors such that unwanted units cancel (m², in²) while desired units remain (g, sheets):

75 g/m² = (75 g/m²)·((8.5 in × 11 in)/(1 sheet))·((2.54 cm)/(1 in))²·((1 m)/(100 cm))²,

75 g/m² = (75 g/m²)·(93.5 in²/sheet)·(6.4516 cm²/in²)·((1 m²)/(10,000 cm²),

75 g/m² = 4.5241845 g/sheet,

or to two significant figures, the mass of a single letter-size sheet of paper is 4.5 g.

(Response (A) is (75·8.5·11)/(10,000·2.54); response (B) is 75·8.5·11·2.54/(10,000); response (D) is 75/(8.5·11·(2.54)²).)

Sections 70854, 70855
Exam code: quiz01CrR4
(A) : 5 students
(B) : 12 students
(C) : 44 students
(D) : 0 students

Success level: 71%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.60