PRACTICE PROBLEM ANSWERS:
1) Which of the following statements is normative and which is positive statement:
“Those who study at least 5 hours for an economics exam earn significantly higher grades.
Therefore, you should study at least 5 hours for this exam.”
The first is a positive (because it’s a statistically verifiable fact) and the second is a normative
statement (because it’s an individual opinion).
2) Use the following table to answer question 2.
Q Marginal Benefit Marginal Cost
1
40.00
20.00
2
25.00
20.00
3
15.00
20.00
4
10.00
20.00
5
0.00
20.00
a.) The table above represents the marginal benefits and marginal costs associated with playing
rounds of golf in a month. How many rounds of golf will this person play?
He’ll play as long as the marginal benefit is greater than the marginal cost, which true for the
first 2 rounds (so Q=2).
b.) If there was a membership cost of $50 to join this golf club, how many rounds will this person
play?
This membership is a sunk cost, so it has no bearing on how many rounds he will play. So the
answer is still Q=2. (Note: Sunk costs never matter. It wouldn’t have changed if the
membership was $100 or $0.)
c.) If marginal costs increased to $26.00 per round, how many rounds would he play?
If the marginal costs increased to $26.00, he would only play 1 round.
3) Describe what the opportunity cost of working on this study guide is to you.
It’s the net benefits you would have received from (or the amount you value) your next best
alternative (what you forego by working on this study guide).
4) A person is choosing between 3 activities, all of which don’t involve any explicit costs. A offers
$20 in benefits, B offers $15 in benefits, and C offers $10 in benefits. Which activity will this
person choose and what is the opportunity cost associated with that activity.
This person will choose Option A, and the opportunity cost is $15 (the net benefits they would have
received from their next best alternative).
5) According to the principle of comparative advantage, everyone does best by specializing in
whatever they have a lower opportunity cost of doing, regardless of their absolute advantages.
6) Use the following production possibilities frontier to answer question 6.
1
ipods
1000
800
500
300
700
850
laptops
Y
The figure above represents the production possibility frontier for ipods and laptops for Apple.
a.) What is the opportunity cost of increasing the production of ipods from 800 to 1000?
400 laptops.
b.) What about the opportunity cost of increasing the production of laptops from 300 to 700?
200 ipods.
c.) What happens to the opportunity cost as we devote more and more resources to the production
of either good?
It’s increasing
90
60
A
30
X
The graph above represents Tom’s PPC for two activities, X and Y.
7a.) The opportunity cost to Tom of doing 1 X is 3 Y.
7b.) The opportunity cost to Tom of doing 1 Y is 1/3 X.
7c.) Point A on the graph above equals 10.
8) Use the following table to answer the following questions:
Joe
Ken
Wheat
50 tons/year
10 tons/year
Rice
25 tons/year
100 tons/year
8b.) Who has a comparative advantage in what?
Joe has a C.A. in wheat production because he has a lower opportunity costs to producing wheat.
Therefore, Ken has a C.A. in rice production
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8c.) How long will it take them in total to produce 200 tons of wheat and 200 tons of rice if they
each produce 100 tons of each?
It will take the Joe 2 years to produce 100 tons of wheat, 4 years to produce 100 tons of rice.
It will take the Ken 10 years to produce 100 tons of wheat, 1 year to produce 100 tons of rice.
8d.) How long will it take them in total to produce 200 tons of wheat and 200 tons of rice if they
only do what they have a comparative advantage in?
It will take the Joe 4 years to produce 200 tons of wheat, Ken 2 years to produce 200 tons of rice.
Important thing here is the most efficient way to produce the two goods is to specialize in what they
have a comparative advantage in.
9.) Use the following demand and supply table to answer the following questions.
Price
Qdemanded
Qsupplied
$0.25
$0.50
$0.75
$1.00
500
400
200
100
200
400
600
800
9a.) What is the equilibrium price and quantity in the market shown above? P=$.50; Q=400
9b.) If the price is currently $0.75, then there will be an excess supply, the market price
will fall, quantity supplied will fall, and quantity demanded will rise.
10) When there is an excess demand (shortage) in a market, what can you predict will happen to
the price, quantity supplied, and quantity demanded in that market?
Excess demand will cause price to increase, quantity demanded to decrease and quantity supplied to
increase until they are equal.
11a) The reservation price to consumers represents their maximum willingness to pay and is based
on benefits.
11b.) The reservation price to consumers represents their minimum willingness to sell and is based
on costs.
12) An individual will buy a good as long as the price is less than their reservation price? A seller
will sell a good as long as the price is greater than their reservation price?
Use the following graph, representing two demand curves to answer question 13:
P
C
B
A
D
Q
13a). Refer to the graph above, and assume it represents a normal good. If consumers see their
incomes decrease, their likely response will best be represented by which arrow?
D (demand is shifting in)
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13b.) Refer to the graph above, and assume it represents an inferior good. If the price of the good
rises, their likely response will best be represented by which arrow?
B (moving upward along the demand; it doesn’t matter whether it’s an inferior good).
14) An increase in “demand” refers to a shifting of the demand curve rightward; an increase in
“quantity demanded” refers to a downward movement along a stationary demand curve?
15) Fill in the blanks to indicate how the following changes will affect supply or demand.
15) Fill in the blanks to indicate how the following changes will affect supply or demand.
15a) An increase in the price of a complement will cause Demand _____ to shift In ______.;
15b) A decrease in income will cause Demand to shift Out for an inferior good.;
15c) An improvement in the technology will cause Supply _____ to shift ______.; Out (right)
15d) An increase in the price of an input will cause _____ to shift ______. Supply; In (left)
15e) An increase in the price of a good will cause ______ to shift _____.
A CHANGE IN THE PRICE OF A GOOD WILL NOT SHIFT EITHER SUPPLY OR DEMAND!
16) The supply of good A is lower than the supply of good B. If the two goods face equal demand
curves, which good will have the higher price? If the market price of good B higher than good A,
what does this mean as far as demand for the two goods?
If they face equal demand curves, the good with the lower supply will have a higher price (A). If
the market price of good B is higher, this implies that the demand for good B is higher than for
good A.
17) Assume the price of milk increases. What do you expect to happen to the equilibrium price
and quantity in the market for cheese (milk is used as an input in the production of cheese)?
Milk is an input in the production of cheese, so supply will decrease. This will cause the
equilibrium price to increase and quantity to decrease.
18) A decrease in equilibrium price and a decrease in equilibrium quantity could be produced by
a(n) decrease in demand, other things constant?
19a.) On a clearly labeled set of axes, illustrate the probable effects of a decrease in the price of
cattle feed, to the supply and/or demand for beef. Start with an equilibrium labeled (Po, Qo) and
label the new equilibrium (P1, Q1).
Explain what changed: Demand or quantity demanded? Supply or quantity supplied?
The decrease in P for cattle feed causes supply for beef to shift out (right).
Supply changed, and quantity demanded changed.
P1<P0 and Q1>Q0;
19b.)Assume after the decrease in the price of cattle feed, the price of chicken increases. What is
the likely effect to the supply and/or demand for beef, if any? Explain what changed: Demand or
quantity demanded? Supply or quantity supplied?
Furthermore, if the new equilibrium is (P2, Q2), do you expect P2 and Q2 to be greater than, less
than, or indeterminate when compared with P1 and Q1?
The increase in the price of chicken causes demand for beef to increase (shift right). Therefore,
demand changed, and quantity supplied changed.
P2>P1 and Q2>Q1
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20) An individual expect to receive $10 in benefits from a good that cost $2 to produce. If the
price of the good is $2, what is the amount of consumer and producer surplus associated with this
transaction?
The consumer surplus is $8 (benefits ($10) – price($2)). The producer surplus is $0 (price ($2) –
costs ($2)).
21) Explain why economists prefer the natural market equilibrium to alternatives such as price
controls?
The market equilibrium maximizes economic surplus (net benefits) to market participants
(consumers and producers). Government interference (such as price controls) take us away from
the natural market equilibrium and result in a reduction in economic surplus.
22) Use the following diagram to answer the following questions.
P
S
100
80
50
30
10
D
500
1000
1500
Q
22a) What is the consumer and producer surplus in the above market associated with the 500th
quantity? CS=$80-$50=$30; PS=$50-30=$20.
22b) What would happen if the government set a price ceiling equal to $30? There would be a
shortage of 1,000 units.
22c) What would happen if the government set a price ceiling equal to $80? Nothing. The price
would be $50.
23) If supply shifts in (to the left) and simultaneously demand shifts out (right), what do you expect
to happen to the equilibrium price and quantity?
Price will definitely increase; quantity may rise, fall, or stay the same.
24) What is the formula for price elasticity of demand?
% change in quantity demanded/% change in price =
(change in quantity /original quantity) / (change in price / original price)
25) If demand is price elastic, this means that the percentage change in quantity demanded is
greater than compared to the percentage change in price.
26) If the price elasticity of demand equals -2.5, a 3% increase in price will have what effect to
quantity demanded?
It will cause quantity demanded to decrease by 7.5% (3%*-2.5).
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27) The price of TVs decreases from $400 to $300 and quantity demanded increases from 6,000 to
7,000. Calculate the price elasticity of demand for TVs using the basic percentage formula. Are
TVs inelastic, elastic or unit-elastic?
elasticity=(% change in quantity / % change in price)
=(1,000/6,000)/(-$100/$400)=.167/-.25=-0.67
TVs are therefore inelastic.
28) Label on the linear demand curve below where it is elastic, inelastic, and unit elastic.
P
$10
$5
20
40
Q
The top half (P>$5 or Q<20) is elastic; the midpoint (P=$5 or Q=20) is unit elastic, and the bottom
half (P<$5 or Q>20) is inelastic.
Use the point-slope method to calculate the price elasticity of demand at a price of $5.
elasticity = (-1/slope)*P/Q = (-1/0.25) * 5/20 = -1
29) As one move upward along a linear demand curve (from the quantity intercept to the price
intercept) price elasticity is increasing in absolute value and revenue is initially increasing until the
midpoint, then decreasing.
30) Draw a perfectly elastic demand curve and perfectly inelastic demand curve. What does the
price elasticity of demand for each equal?
Perfectly elastic demand curves are horizontal and have a price elasticity equal to infinity.
Perfectly elastic demand curves are vertical and have a price elasticity equal to zero.
31) Determine whether demand for the following goods are elastic, inelastic, or unit elastic:
a.) Price increases by 10% and revenue increases by 10%. INELASTIC.
b.) Price increases by $10 and revenue decreases by 12%. ELASTIC.
c.) Price increases by 10% and quantity demanded decreases 10 units. INDETERMINATE
d.) Price decreases by 10% and revenue doesn’t change. UNIT ELASTIC.
e.) Price decreases by 10% and revenue increases from $400 to $500. ELASTIC.
f.) Price decreases by 5% and quantity demanded increases by 5% UNIT ELASTIC.
32) A good has a price elasticity equal to -0.6 and quantity demanded is 10,000. What is the new
quantity demanded when price decreases by 10%? What will happen to total revenue (will it
increase or decrease)?
Quantity demanded will increase by -0.6*-10%=6% such that the new quantity demanded will be
10,000 + 10,000*6% = 10,600.
Total revenue will decrease because it is inelastic and price decreased.
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33) Income increases by 3% and quantity demanded decreases from 100 to 95. What is the income
elasticity of demand for this good? Is it a normal or inferior good?
EI = -5% / 3% = -1.666. It’s inferior
34) The cross price elasticity between good B and C is +2, and the price of good C decreases by
6%. What happens to the quantity demanded for good B? Are these goods complements or
substitutes?
Quantity demanded for good B decreases by 12% (-6%*2). Goods B and C are substitutes.
35) Is the cross-price elasticity positive or negative for the following items?
a. tuna and peanut butter. Positive (because they are substitutes).
b. beer and pretzels. Negative (because they are complements).
36) Fill in the blank with “positive” or “negative”
The income elasticity of demand is positive for a normal good, and negative for an inferior good;
the cross price elasticity is negative for complements and positive for substitutes; the price
elasticity of supply is positive.
Note: The answer to the first extra credit question is Elinor Ostrom.
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