# 2.1 How individuals make choices based on their budget constraint  (Page 2/16)

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## The concept of opportunity cost

Economists use the term opportunity cost    to indicate what must be given up to obtain something that is desired. The idea behind opportunity cost is that the cost of one item is the lost opportunity to do or consume something else; in short, opportunity cost is the value of the next best alternative. For Alphonso, the opportunity cost of a burger is the four bus tickets he would have to give up. He would decide whether or not to choose the burger depending on whether the value of the burger exceeds the value of the forgone alternative—in this case, bus tickets. Since people must choose, they inevitably face tradeoffs in which they have to give up things they desire to get other things they desire more.

View this website for an example of opportunity cost—paying someone else to wait in line for you.

A fundamental principle of economics is that every choice has an opportunity cost. If you sleep through your economics class (not recommended, by the way), the opportunity cost is the learning you miss from not attending class. If you spend your income on video games, you cannot spend it on movies. If you choose to marry one person, you give up the opportunity to marry anyone else. In short, opportunity cost is all around us and part of human existence.

The following Work It Out feature shows a step-by-step analysis of a budget constraint calculation. Read through it to understand another important concept—slope—that is further explained in the appendix The Use of Mathematics in Principles of Economics .

## Understanding budget constraints

Budget constraints are easy to understand if you apply a little math. The appendix The Use of Mathematics in Principles of Economics explains all the math you are likely to need in this book. So if math is not your strength, you might want to take a look at the appendix.

Step 1: The equation for any budget constraint is:

where P and Q are the price and quantity of items purchased and Budget is the amount of income one has to spend.

Step 2. Apply the budget constraint equation to the scenario. In Alphonso’s case, this works out to be:

Step 3. Using a little algebra, we can turn this into the familiar equation of a line:

For Alphonso, this is:

Step 4. Simplify the equation. Begin by multiplying both sides of the equation by 2:

Step 5. Subtract one bus ticket from both sides:

$\begin{array}{rcl}{\text{20 – Q}}_{\text{bus tickets}}& \text{=}& {\text{4 × Q}}_{\text{burgers}}\end{array}$

Divide each side by 4 to yield the answer:

$\begin{array}{rcl}{\text{5 – 0.25 × Q}}_{\text{bus tickets}}& \text{=}& {\text{Q}}_{\text{burgers}}\\ & \text{or}& \\ {\text{Q}}_{\text{burgers}}& \text{=}& {\text{5 – 0.25 × Q}}_{\text{bus tickets}}\end{array}$

Step 6. Notice that this equation fits the budget constraint in [link] . The vertical intercept is 5 and the slope is –0.25, just as the equation says. If you plug 20 bus tickets into the equation, you get 0 burgers. If you plug other numbers of bus tickets into the equation, you get the results shown in [link] , which are the points on Alphonso’s budget constraint.

Point Quantity of Burgers (at $2) Quantity of Bus Tickets (at 50 cents) A 5 0 B 4 4 C 3 8 D 2 12 E 1 16 F 0 20 Step 7. Notice that the slope of a budget constraint always shows the opportunity cost of the good which is on the horizontal axis. For Alphonso, the slope is −0.25, indicating that for every four bus tickets he buys, Alphonso must give up 1 burger. There are two important observations here. First, the algebraic sign of the slope is negative, which means that the only way to get more of one good is to give up some of the other. Second, the slope is defined as the price of bus tickets (whatever is on the horizontal axis in the graph) divided by the price of burgers (whatever is on the vertical axis), in this case$0.50/\$2 = 0.25. So if you want to determine the opportunity cost quickly, just divide the two prices.

No question... This is nice
hw can we solve problem of scarcity
Oigebe
scarcity is not necessarily a problem but a constant condition of the world. there are not enough resources to satisfy the unlimited wants.
Matthew
why do compute GDP?
can anyone shortly determine the word inflation.
Continous increase in the general level of prices or in the cost of living.
persistent increased in general price level
Machall
all correct...
paa
the father of economics
sj
Ajit
the father of economic regarding to adam Smith
Ibrahim
the father of political of economic and capitalism in his book and inquary in to the wealth of the nation.
Umar
Adam Smith his the father of economic
Mamudu
different types of price elasticity of demand with the aid of graphs
what about mean median and mode
mode is the most occurred number and median is the middle digit
John
the mean is the sum of all the data divided by the number eg: 2+4+4+5+3+5+1 =24÷7
BEGE
economics
ghani
what is exchange rate
Festo
thanks guys
Runwell
What is Equilibrium?
Santos
that when supply equals demand. that's where the supply curve and the demand curve intercept.
equilibrium is when the both side of the price is balanced
Asuquo
Thanks Asuquo Agwuu
Santos
lungku
it's thrift not drift
lungku
so what is it sir
Festo
what are the causes of unemployment
lack of job in the rural areas
Nicholas
High level of illiteracy
Unfulfilled government promises
Vee
this one no be problem waii
Nicholas
low rate of industrialisation
Mimi
elements of economic
Supply demand consumer and money.
what is economic growth
Good morning. It is within a period of time that goods and services increase to become more efficient.
Hughes
Economic growth is also the growth of income and it can take place under conditions of high unemployment and general poverty.......
favour
favour
Abdul
what is human capital formation
Thato
It deals with humans behavior
Afful
Can someone mention the types of unemployment
Afful
Interest
Afful
income inequality and poverty can be included as social economy
Festo
what is the relationship btn indifference curve and consumer utility maximization
Festo
what is the the law of diminishing marginal utility
Doris
pls one question at a time
Nicholas
the law of diminishing marginal utility states that , the more a commodity possessed les satisfaction is derived from it
Festo
structural unemployment, seasonal unemployment, disguised unemployment,
Festo
each indifference curve has its own level of satisfaction and for consumer utility maximization a budget line should be tangent to indeference curve.
Festo
let's discuss together guyz come on
Festo
can any one mention elements of economic
start it then
Doris
Festo
Doris I don't understand about human capital formation, so how do u understand it?
Festo
national income means MKT value of all final goods en services in particular particular period of time usually a year
Festo
The transformation of raw human resource into highly productive human resource with these input. Human resource can be turned into human capital with effective input.
Doris
Muhammad, as in environmental sense ?
Hughes
From my understanding I am currently taking up Econ 302 Principles of Economics. There's 3 that I know of. 1. Traditional 2. Command 3. Market
Hughes
What is National incoming Accounting
Intrested
yassine
National income accounting is the aggregate data use to major the well being of an economic.
Ibrahim
What's Bank?
A bank is A Financial institution that accepts the deposit from the public and lending this money to the public in the form of loans and advances
xaid
A bank is as well an institution that manages the flow of the currency
sbu
A bank is the place where banking activities is been carried out.
Nicholas
And a bank is where treasures goods are kept and must be insured.
BEGE
banking and a Bank are two different things
Nicholas
banking is the act of accepting money as deposit, giving of loans, and keeping treasure bills for consumers
Nicholas
a bank is a financial institute that accepts deposit n give out loan
doris
a bank is a place where transactions are taking place.
Ibrahim