(function(weight) {
    // how much water weighs per gallon
    const WATER_WEIGHT_IN_POUNDS_PER_GALLON = 8.34;
    // how much of the body is made of water
    const WATER_PERCENTAGE_IN_BODY = 0.6;

    function getGallonsOfWater(weight) {
        return weight * WATER_PERCENTAGE_IN_BODY / WATER_WEIGHT_IN_POUNDS_PER_GALLON;
    }

    function getPoundsFromGallons(gallons) {
        // since water is 60%, we need to figure out the other 40%
        // so we just find one third of 60% (20%) and then double that
        // to find 40% and add the two together to uncover what the original
        // weight was
        const oneThird = gallons / 3;
        return (gallons + (oneThird * 2)) * WATER_WEIGHT_IN_POUNDS_PER_GALLON;
    }

    console.clear();
    console.log({
        weight,
        gallons: getGallonsOfWater(weight),
        andBack: getPoundsFromGallons(getGallonsOfWater(weight))
    });
}
)(200);