Question

Karin observed that water level in the part of the river she observed fell 1.68 millimeters per year for 1.5 years

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Answer 1

It is given that the water level in the part of the river fell 1.68 millimeters per year. The exact variation in water level for one year time period is -1.68. Therefore the exact variation in water level for the time period is -2.52 millimeters.