## 20170917

### Physics quiz question: average speed of John Muir unsupported FKT

Physics 205A Quiz 1, fall semester 2017
Cuesta College, San Luis Obispo, CA

"John Muir Trail Fastest Known Time"
Andrew Bentz
youtu.be/r7PbffxyKLw

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

210.4 mi ÷ 82.9944 h = ?

(A) 2.53511 mi/h.
(B) 2.5351 mi/h.
(C) 2.535 mi/h.
(D) 2.5 mi/h.

Correct answer (highlight to unhide): (C)

(This is the average speed of Andrew Bentz's fastest known time for an unsupported hike of the John Muir Trail in August 2014.)

210.4 mi has four significant figures, while 82.9944 h has six significant figures, as denoted in green.

For multiplication and division operations, the term with the least number of significant figures determines the number of significant figures in the result, so the resulting calculation is limited to four significant figures:

(210.4 mi)/(82.9944 h) = 2.351108027 mi/h,

and thus the result should be truncated to show only four significant figures, as given by 2.351 mi/h.

Sections 70854, 70855
Exam code: quiz01D4mP
(A) : 1 student
(B) : 1 student
(C) : 53 student
(D) : 3 students

Success level: 91%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17