1/19/17, 4(13 PM
Assignment Results
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Score:
Score:
50/50
Points
100
%
Single Variable Equations
Single Variable Equations
Solving an equation when only one variable is unknown is straightforward.
It is just a matter of
isolating the unknown variable on one side of the equals sign.
For example, we could use the equation for output in an open economy (Y = C + I + G + NX) to solve
for Investment
'I'
'I'
when consumption 'C'
is $104.6, output 'Y' is $182.5, government spending 'G' is
$48.8 and net exports 'NX' is -$5.2.
All numbers are in billions.
First, we start with our equation:
Y = C +
I
I
+ G + NX
And plug in the values we are given (we will leave out the “billions” label until the end, since all
numbers are expressed in the same terms).
Note that adding a negative number is the same as
subtracting a positive number, as on the NX term:
$182.5 = $104.6 +
I
+ $48.8 - $5.2
Now group together the constants on the right-hand side:
$182.5 = $104.6 + $48.8 - $5.2 +
I
$182.5 = $148.2 +
I
And get the unknown variable
I
on one side by itself by subtracting $148.2 from both sides:
$182.5 - $148.2 =
I
And simplify to solve for I:
I
=
$34.3 billion

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