To find out how much $100 today is equivalent to in 1975 dollars, we can use the Consumer Price Index (CPI).
Here are the steps to convert the current amount to the past amount:
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Identify the CPI values:
- CPI in 1975 = 90
- CPI today = 225
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Use the formula to find the equivalent amount in 1975: \[ \text{Equivalent amount in 1975} = \text{Amount today} \times \left(\frac{\text{CPI in 1975}}{\text{CPI today}}\right) \]
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Plug in the values: \[ \text{Equivalent amount in 1975} = 100 \times \left(\frac{90}{225}\right) \]
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Calculate: \[ \frac{90}{225} = 0.4 \] \[ \text{Equivalent amount in 1975} = 100 \times 0.4 = 40 \]
So, $100 today is equivalent to $40.00 in 1975.
The correct answer is: c. $40.00 purchased in 1975.