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## Homework Statement

The radius of a sphere is measured to be (6.90 0.25 ) cm, and its mass is measured to be (1.75 0.05) kg. The sphere is solid. Determine its density in kilograms per cubic meter and the uncertainty in the density. (Use the correct number of significant figures.)

## Homework Equations

Volume = (4/3) (pi)(radius)^3

= (4/3) (3.1416)(6.9/100)^3 = 1.376 X 10^-3 m^3

Density = mass / vol = 1.75 / 1.376 X 10^-3 = 1271.8 kg / m^3

= 1.27 X 10^3 kg /m^3

## The Attempt at a Solution

% error in radius = (0.25/6.9)X100 = 3.6%

therefore % error in volume = 3 X 3.6% = 10.8%

% error in mass = (0.05/1.75) X 100 = 2.86%

So % error in the density = 10.8 + 2.86 = 13.66%

Therefore undertainty in density = 13.66% of 127 X 10^3 kg/m^3

= 173 kg/m^3

So density = (1.27±0.173) X 10^3 kg/m^3

According to webassign, my answer is incorrect. I can't figure out what I did wrong. Any help would be appreciated.