| Course | ECON 1002 Microeconomics |
|---|---|
| Week | Week 4 |
| Paper type | Problem set write-up |
| Length | About 790 words, 5 pages |
| Format | APA 7 student paper |
| School | Walden University |
| Program | BS in Business Administration |
| Updated | October 2026 |
Free sample paper for ECON 1002 Week 4
Four Problems on a Weekly Schedule for Secondhand Bicycles, Each Worked Line by Line and Closed With a Plain Statement About Buyers or Sellers: Equilibrium, a Surplus at $160, Elasticity and Consumer Surplus
Student Name
Walden University
ECON 1002: Microeconomics
Instructor Name
Month Day, Year
Four Problems on a Weekly Schedule for Secondhand Bicycles, Each Worked Line by Line and Closed With a Plain Statement About Buyers or Sellers: Equilibrium, a Surplus at $160, Elasticity and Consumer Surplus
The Schedule
All four problems use the weekly schedule below for secondhand commuter bicycles in a small town. The schedule is illustrative and was supplied in the assignment packet; demand follows the rule quantity demanded = 95 − 0.5 x price, and supply follows quantity supplied = 0.5 x price − 25.
Table 1
Weekly Demand and Supply Schedule for Secondhand Bicycles
| Price | Quantity demanded | Quantity supplied | |
|---|---|---|
| $80 | 55 | 15 | |
| $100 | 45 | 25 | |
| $120 | 35 | 35 | |
| $140 | 25 | 45 | |
| $160 | 15 | 55 | |
| $180 | 5 | 65 | |
Source: assignment packet schedule, illustrative.
Problem 1: Equilibrium
Question. Find the equilibrium price and quantity.
Working. Equilibrium is where quantity demanded equals quantity supplied. Setting 95 − 0.5P = 0.5P − 25 gives 120 = P, so P = $120. Substituting, quantity demanded = 95 − 60 = 35 and quantity supplied = 60 − 25 = 35. The table confirms it: at $120 both columns read 35.
Meaning. At $120 a week, every buyer willing to pay that price finds a bicycle and every seller willing to accept it finds a buyer. Thirty-five bicycles change hands each week, and there is no pressure on price to move.
Problem 2: A Surplus at $160
Question. If sellers hold their asking prices at $160, what happens?
Working. At $160, quantity supplied = 0.5(160) − 25 = 55 and quantity demanded = 95 − 0.5(160) = 15. The surplus is 55 − 15 = 40 bicycles a week.
Meaning. At $160, forty more bicycles are listed each week than buyers want. Listings would sit for weeks, and sellers who need to sell would cut their prices. The surplus is what pushes the price back toward $120. Only fifteen bicycles actually sell, fewer than at equilibrium, because buyers, not sellers, decide how many trades happen when the price is above equilibrium.
Problem 3: Elasticity Between $100 and $120
Question. Using the midpoint method, find the price elasticity of demand between $100 and $120, and say what it suggests.
Working. The change in quantity is 35 − 45 = -10, and the midpoint quantity is (45 + 35) / 2 = 40, so the percentage change in quantity is -10 / 40 = -25 percent. The change in price is 120 − 100 = 20, and the midpoint price is (100 + 120) / 2 = 110, so the percentage change in price is 20 / 110 = 18.2 percent. Elasticity = -25 / 18.2 = -1.37, or 1.37 in absolute value.
Meaning. Demand is elastic in this price range: a price rise of about 18 percent cuts the number of bicycles bought by about 25 percent. Buyers here are fairly sensitive to price, which makes sense for a used good with substitutes such as walking, the bus or a cheaper bicycle. Greenlaw et al. (2022) explain why the midpoint method is used: it gives the same answer whether the price rises or falls between the two points.
Problem 4: Consumer Surplus at Equilibrium
Question. Calculate consumer surplus at equilibrium and explain what it represents.
Working. Consumer surplus is the area below the demand curve and above the price, out to the quantity bought. Demand reaches zero where 95 − 0.5P = 0, so P = $190; that is the highest price any buyer would pay. The area is a triangle with height 190 − 120 = $70 and base 35 bicycles: 0.5 x 70 x 35 = $1,225 a week.
Meaning. Buyers as a group value the 35 bicycles they buy each week at $1,225 more than they pay for them. The first buyer would have paid up to $190 and paid $120, keeping $70; the 35th buyer valued the bicycle at almost exactly $120 and gained almost nothing. Consumer surplus measures the benefit buyers get from the market beyond what they spend (Mankiw, 2021), an idea that goes back to Marshall (1890).
A Note on the Four Results
Read together, the problems describe one market. It settles at $120 and 35 trades a week; a price held above that point leaves a surplus and fewer trades; buyers respond strongly to price in the range just below equilibrium; and the trades that do happen create about $1,225 a week in value for buyers. Each statement can be checked against the schedule without redoing the arithmetic. They also show why a write-up needs words as well as numbers: a reader who sees only "$1,225" or "1.37" learns nothing about buyers until someone says what the figure means.
References
Greenlaw, S. A., Shapiro, D., & MacDonald, D. (2022). Principles of microeconomics (3rd ed.). OpenStax. https://openstax.org/details/books/principles-microeconomics-3e
Mankiw, N. G. (2021). Principles of microeconomics (9th ed.). Cengage Learning.
Marshall, A. (1890). Principles of economics. Macmillan.
ECON 1002 Week 4 instructions, in plain terms
In Week 4 you solve a set of supply and demand problems and explain each result in words. For every problem, restate the question, show the working step by step and then write a short paragraph saying what the answer means for buyers, sellers or the market. Use the midpoint method for elasticity and explain why. Label areas such as consumer surplus clearly and say what they measure. Cite the source of the data, usually the assignment packet. Correct arithmetic without interpretation earns only half the credit, and an interpretation without visible working cannot be checked.
How the ECON 1002 Week 4 example is put together
The write-up opens with the schedule and the linear rules behind it, noting that the figures come from the packet. Problem one sets the two rules equal and confirms the answer against the table. Problem two computes quantity supplied and demanded at $160 and explains why the surplus pushes the price down and why only fifteen bicycles sell. Problem three calculates midpoint percentage changes of 25 and 18.2 percent and interprets the elasticity as fairly price-sensitive buyers, citing OpenStax on the method. Problem four finds the choke price of $190 and the triangle area, then explains surplus from the first buyer to the thirty-fifth, citing Mankiw. A closing note reads the four results as one market.
Where the marks sit in the ECON 1002 Week 4 rubric
Problem sets are graded for accuracy and for interpretation. Each step of the working should be visible and correct, with units. The interpretation must state what the number means in terms of real buyers or sellers; "elasticity is 1.37" is not an interpretation. Using the midpoint method, and saying why, is expected for elasticity. Consumer surplus should be identified as an area and explained as what buyers would have paid minus what they actually paid. Strong write-ups notice what the results show together, such as why fewer trades happen at a price above equilibrium. Sloppy units, missing steps or unexplained numbers lose credit quickly. Presentation counts too: each problem should be numbered and laid out the same way, so a grader can find the working and the meaning at a glance without hunting.
ECON 1002 Week 4 help: mistakes that cost marks
Work each problem on scrap paper first, then copy the steps neatly in order. After each answer, stop and ask: who does this number describe, and what does it say about them? Write that sentence. For elasticity, remember to divide by the average of the two values, not the starting value. For consumer surplus, find where demand reaches zero; that is the top of the triangle. Check your answers against the schedule wherever you can. Common slips include reversing quantity supplied and demanded and forgetting that only the smaller of the two is actually traded. Share your schedule and we can work a model set from it.
Get a ECON 1002 Week 4 example written to your instructions
Attach the problem set itself with its rubric, and each problem is worked on your numbers and then explained, back in 24 to 48 hours, the first one free. This schedule of bicycle prices was invented for practice, and no seller's listings supplied a single row of it.
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ECON 1002 Week 4 questions, answered
Where can I find a free ECON 1002 Week 4 sample paper?
All four worked problems, with their interpretations, are posted below at no cost.
What is the equilibrium in the ECON 1002 Week 4 problem set?
$120 a week, where thirty-five bicycles are both offered and wanted.
What happens if sellers hold out for $160?
Fifty-five bicycles are listed but only fifteen are wanted, a surplus of forty that pushes the price back down.
What does the elasticity of 1.37 mean?
Demand is elastic between $100 and $120: an 18 percent price rise cuts purchases by about 25 percent.
How is consumer surplus calculated?
As the triangle between the demand curve and the $120 price, out to thirty-five bicycles: half of $70 times 35, or $1,225 a week.