The seven fundamental SI units are: - ampere - mole - kelvin - kilogram - second - meter - candela

All others are considered derived units.

The radius of the earth is approximately \(10^4 km\), which is \(10^7 m\).

significant figure consistency

significant figures do not count leading zero.

use significant figure in multiplication, 相乘选择最小significant figure; decimal places in add

inversely proportional: \(y\propto \frac{1}{x}\)

controlled variable, independent variable

best fit line can be a curve

prove proportional: - straight line - pass through origin