Dividing a gallon into tenths is easy. Pour it into a measuring cup until it's at 1/10th of a gallon. With sand by weight, pour it onto a balance until you get

Dividing a gallon into tenths is easy. Pour it into a measuring cup until it's at 1/10th of a gallon. With sand by weight, pour it onto a balance until you get your desired weight. Easy peasey.