You use 4 gallons of water on 30 plants in your garden. at that rate, how much water will it take to water 45 plants

4 gallons of water ... 30 plants
x gallons of water = ? ... 45 plants

If you would like to know how much water will it take to water 45 plants, you can calculate this using the following steps:

4 * 45 = x * 30
180 = 30 * x    /30
x = 180 / 30
x = 6 gallons of water

Result: You will use 6 gallons of water to water 45 plants.