In 28 days, a clysedale would drink about 840 gallons of water. Due to the fact that clysedale drinks 120 gallons of water every 4 days, you would first find the number of gallons that it can drink in one day, so 120 divided by 4 equals 30, so the horse drinks 30 gallons of water a day. To find out how many many gallons the clysdale would drink in 28 days, you need to multiply 30 by 28, to find the answer of 840.