Find the missing value.
main drive gear = 45 teeth
speed of main drive gear = 450 r. p.m.
countershaft drive gear = 70 teeth
speed of countershaft drive gear (to the nearest tenth) = ? r. p.m.

To calculate the speed of the 70 teeth countershaft drive gear, evaluate the surface teeth per minute (STM) of each gear. STM = Speed x number of teeth, which is equivalent for both gears. Thus, 45 teeth * 450 r.p.m. = 70 teeth * 'x' r.p.m. is the governing equation. Rearranging the equation to calculate 'x' as the 70 teeth gear's speed, the answer is  289.3 r.p.m.

Ithink its 126 hope its