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Inflation index & Model K mixer

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by GmatGreen » Fri Feb 14, 2014 12:12 pm
The inflation index for the year 1989 relative to the year 1970 was 3.56, indicating that, on the average, for each dollar spent in 1970 for goods, $3.56 had to be spent for the same goods in 1989. If the price of a Model K mixer increased precisely according to the inflation index, what was the price of the mixer in 1970?

1) The price of the Model K mixer was $102.40 more in 1989 than in 1970

2) The price of the Model K mixer was $142.40 in 1989
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Source: — Data Sufficiency |
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by Patrick_GMATFix » Fri Feb 14, 2014 12:36 pm
This is a ratio. Every dollar spent in 1970 corresponds to 3.56 dollars in 1989. So we can express the price of both years in terms of the same variable: p and 3.56p. Data about any relationship between the two prices will result in an equation that has only one variable, and that we can likely solve!

The full solution below is taken from the GMATFix App.

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by [email protected] » Fri Feb 14, 2014 12:37 pm
Hi GmatGreen,

The prompt for this DS question tells us that if an item cost $X in 1970, then that same item cost (3.56)($X) in 1989. We're asked what the price of a mixer was in 1970; which essentially asks for the value of X.

Fact 1: The price of the mixer was $102.40 MORE in 1989 than in 1970

Combining this info wit what we were given from the prompt, we have:

(3.56)($X) - $X = 102.40

Since this one equation has just one variable, we CAN solve for X (there would be just one solution, so we don't need to do the math).
Fact 1 is SUFFICIENT

Fact 2: The price of the mixer was $142.40 in 1989

Combining this info with what we were given from the prompt, we have:

(3.56)($X) = 142.40

Again, we have one variable and one equation, so we CAN solve for X.
Fact 2 is SUFFICIENT

Final Answer: D

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