Problem: circular gears l and r start to rotate at the same time at the same rate . gear l makes 20 complete revolutions per minute and gear r makes 60 revolutions per minute . how many seconds after the gears start to rotate will gear r have made exactly 8 more revolutions than gear l ?
Rationale: "gear l - - 20 rotations per 60 seconds - - 2 rotation per 6 seconds . gear r - - 60 rotations per 60 seconds - - 6 rotations per 6 seconds . first 6 seconds - - gear l makes 1 rotation . - - gear r makes 4 rotations - - net difference - - 4 rotations hence every 6 seconds the difference between the number of rotations of r and l gear is 4 units . required net difference should be 8 rotations = > 2 ( 6 seconds later ) = = > 12 seconds . answer : e"
annotated_formula: divide(divide(8, subtract(divide(60, const_60), divide(20, const_60))), const_3)