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Chapter 5 Problem Set: Using Equations to Describe a Relationship
1. Explain in words what the following relationships mean:
a. A + B = C + D
b. A = C
B D
2. Solve each of the following equations for X. Express your answer
with the appropriate units.
a. 2X = 14
b. X = 2.5 cm (55 cm – 45 cm)
c. -2X = 0.3X – 10.0 mg
d. 20 = X
10 50
e. 0.45 cm = 25 cm
X
50 g
f. 0.45 g = 25 cm
X
50 g
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g. X = 2.5 mg (0.445 mL) 30 oz
mL
mg
h. Are the answers to 2e and 2f the same? Explain.
3. Translate the following words into an algebraic equation:
a. Five more than twice some number is 45.
b. Some number divided by the sum of itself and six is one-half.
4. The sum of twice a number and 5 is 25. Write the equation that
describes the situation. THEN find the number.
5. The sum of twice a number and 6 is two less than three times the
number. Write the equation that describes the situation. THEN
find the number.
6. The cost of a particular enzyme is $150 for the first 100 mg and $10
for every additional 10 mg. If the total cost of an order is $250, how
many mg were ordered?
7. Solve the following expressions. REMEMBER ORDER OF
OPERATIONS!!!! Note that X is not an unknown here—it stands
for multiplication!!!!
a. 25 – 2(3 X 2 – 4) + 10 = ___________
b. (0.4 X 10-3 X 4.0) + 7 = ___________
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c. 23 X 44 = ___________
d. (52)(33) / 20 = ___________
e. 53 – 21 = ___________
f. 51 / 34 = ___________
g. (-0.3)2 + 9.62 = ___________
h. (725 X 102)(0.0200) = ___________
(3.7 X 103)
i. (9.30 X 103) + (4.22 X 10-2) = ___________
(8.8 X 108)(6.0 X 10-6)
j. 4.5 X 103 + 2.7 X 10-2 = ___________
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8. An important equation in centrifugation is:
RCF = 11.18 X r(RPM/1000)2
RCF is the force experienced by an object in a centrifuge. RPM is
“revolutions per minute”, that is, the number of times the object spins in a
complete circle each minute. “r” stands for the “radius of rotation” which
relates to how far the object is from the center of the centrifuge.
a. As a centrifuge spins faster, what happens to the force experienced by
an object in that centrifuge?
b. What happens to the force experienced by an object if “r” is
decreased?