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Symmetric deviations from a level

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A price level is $200$ . $2$ readings sit at $205$ and $195$ . Find the difference between the square of the higher reading and the square of the lower reading.

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Hint

Both readings are the same distance from $200$ .

Solution

The required value is $20 5^{2} - 19 5^{2}$ .
Factor: $(205 - 195) (205 + 195)$ .
That is $10 \times 400$ .
The difference is $4000$ .

Answer: $4000$

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