Physics for Scientists & Engineers & Modern Physics, 9th Ed

 Significant figure guidelines 
used in this book
Pitfall Prevention 1.5
Symbolic Solutions When solving 
problems, it is very useful to per-
form the solution completely in 
algebraic form and wait until the 
very end to enter numerical values 
into the final symbolic expres-
sion. This method will save many 
calculator keystrokes, especially if 
some quantities cancel so that you 
never have to enter their values 
into your calculator! In addition, 
you will only need to round once, 
on the final result.
Summary
Definitions
The three fundamental physical quantities of 
mechanics are length, mass, and time, which in the SI 
system have the units meter (m), kilogram (kg), and 
second (s), respectively. These fundamental quantities 
cannot be defined in terms of more basic quantities.
The density of a substance is defined as its mass per 
unit volume:
r
;
m
V
(1.1)
Example 1.5 
Installing a Carpet
 
A carpet is to be installed in a rectangular room whose length is measured to be 12.71 m and whose width is measured 
to be 3.46 m. Find the area of the room.
If you multiply 12.71 m by 3.46 m on your calculator, you will see an answer of 43.976 6 m
2
. How many of these num-
bers should you claim? Our rule of thumb for multiplication tells us that you can claim only the number of significant 
figures in your answer as are present in the measured quantity having the lowest number of significant figures. In this 
example, the lowest number of significant figures is three in 3.46 m, so we should express our final answer as 44.0 m
2
.
S o L u t i o n
continued

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