Also, the name **sanity test** has been used to refer to various order of magnitude and other rule of thumb devices applied to mathematical calculations. 738^{2} cannot be equal to 53,874 since 300^{2} is 90,000; the power output of a car cannot be 700 kJ since that is a unit of energy, not power (energy per unit time) and 918 x 155 is not 142135 since 918 divides by three but the answer does not (digits do not add up to a multiple of three).