Explain why you can multiply both the numerator and denominator by the same number

Several processes form metal ore. match each process to its description. volcanic activity weathering hydrothermal energy rocks break down as they interact with air and water. arrowright density differences and other factors cause metals to concentrate in igneous rocks. arrowright seawater heats up from contact with hot rock, and metals dissolve in it. the water rises and contacts cooler water, causing metal ores to settle on the ocean floor. arrowright

The density of a liquid could be found by using

Automobile fuel efficiency is often measured in miles that the car can be driven per gallon of fuel (mpg). heavier cars tend to have lower fuel efficiencies (lower mpg ratings). which variable (weight or fuel efficiency) is most naturally considered the explanatory (predictor) variable in this context?