A potassium isotope has a half-life of 1.25 billion years. Given that scientist estimate earths age to be 4.6 billion years what is the most likely percentage of parent to daughter isotopes this element currently existing on earth?

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.