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QUIZ 1.
1. (5 points) The one troy ounce (31.1035 g) Credit Suisse gold bar is a convenient size
that is popular with gold bar buyers worldwide. The size of the bar is approximately
4.20 cm long, 2.4 cm wide and 0.16 cm thick. Calculate the density of gold to the correct
significant figures.
d=
m
V
d=
31.1035 g
g
= 19.285 = 19 3
4.20cm × 2.4cm × 0.16cm
cm
V = length × width × depth
The number of significant figures in the result is set by the original number that has the
smallest number of significant figures (in this case either 2.4 cm or 0.16 cm).
2. (5 points)
a. How many significant figures are in each of the following measured numbers?
i) 1.00030 cm
ii) 6.023 x 1023
6
4
Zeros between nonzero digits are significant
If a number is greater than 1, then all zeros to the right of the decimal point are
significant
b. Round each of the following numbers to four significant figures and express the result
in standard exponential notation (scientific notation).
i) 0.0000027
ii) 934.2
2.700×10-6
9.342×102
3. (5 points) In order to describe the color of the bulb light, the color temperature in
degrees Kelvin is used. Many fluorescent indoor lamps have a “cool” temperature range
of 4000-5000 K. Convert the color temperature of the fluorescent light bulb of 4700 K
into oC and oF.
? oC = K – 273
4700K – 273 = 4427oC
9
× 4427 oC + 32 = 8000 o F
5
? oF =
9o
C + 32
5
4. (5 points) Carry out the following operations and express the answers with appropriate
number of significant figures:
i) 87.7265 ÷ 41.3 = 2.12
For the division and multiplication the number of significant figures in the result is set by
the original number that has the smallest number of significant figures (3 significant
figures in the 41.3)
ii) (3.985 + 23.02) × (6.872 – 7.2) = 27.01 × -0.3 = -8
For addition and subtraction the answer cannot have more digits to the right of the
decimal point than any of the original numbers. For the division and multiplication see
above.
5. (5 points) Convert the speed limit of 70 mi/hr on the Mississippi interstates into m/s (1
mile = 1609 m).
70
mi 1609m 1 hr
m
1 min
×
×
×
= 31
hr
1 mi
60 min 60 s
s
BONUS (10 points). The efficiency of the car in the US is expressed in miles per gallon
(mpg, or mi/gal) of gas a car can drive. In Europe, however, the efficiency is expressed in
how much fuel (in liters, L) is consumed per 100 km. Convert the efficiency of the car
with 28 mpg into European standard in L/100km. (1 mile = 1.609 km, 1 gallon = 3.785
L).
28
mi 1.609km 1gal
km
×
×
= 11.9
gal
1 mi
3.785 L
L
Invert the result:
1
11.9
km
L
=
1 L
L
= 0.084
11.9 km
km
Multiply both numerator and denominator by 100:
0.084
L 100
L
×
= 8.4
km 100
100km