Addition and Cola
a.) Sara’s income is expressed as the quantity of goods that she can afford to buy. Expressed in terms of cola, Sara’s real income is 4 cans of cola. We divide the money income $12 by the price of cola $3.
$12 / $3 = 4
b.) The same here: Expressed in terms of popcorn, Sara’s real income is 4 bags of popcorn. Again, we divide the money income $12 by the price of popcorn $3.
$12 / $3 = 4
c.) A relative price is the price of one good divided by the price of another good. The price of popcorn is $3 per bag and the price of cola is $3 per can. To find the relative price, we divide the price of cola $3 by the price of popcorn $3. So the relative price of cola is 1 bag of popcorn per can of cola.
$3 / $3 = 1
d.) Sara must give up 1 bag of cola because in this case we see that a can of cola is equal to a bag of popcorn.
e.) The budget equation starts with:
Expenditure = Income
Expenditure is equal to the sum of the price of each good multiplied by the quantity bought.  the price of popcorn= PP
 the quantity of popcorn= QP
 the price of cola= PC
 the quantity of cola= QC

Sara’s budget equation is:PPxQP + PCxQC = Y, or we use the prices of goods. We get:$3QP + $3QC = $12 To find the relationship between these quantities we divide both sides of the equation by $3, and we get:QP + QC = 4
Now, we will subtract QC from both sides to obtain:QP = 4 – QC(that is the equation for Sara’s budget line).
f.)
Popcorn (per week)
4
 Budget line
Affordable Unaffordable
0 4 Cola (per week)
g.) To calculate the slope of a straight line, we divide the change in the value of the variable measured on the yaxis by the change of the variable measured on the xaxis. Therefore,...
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