Casey is pumping water out of her well. She can pump 3 gallons a minute. She has 4 rows of 15 corn plants each, and each plant needs half a gallon of water. She also has 10 pigs, which each need 4 gallons of water, and 20 ducks that each need a quarter of a gallon of water. How many minutes does Casey need to spend pumping water?
Let's be accurate as possible. Think before you answer.
25
First find how many corn plants there are: 15 plants / row * 4 rows = 60 plants.

Then find how many gallons of water of the corn needs: 60 plants * 1 / 2 gallon / plant = 30 gallons.

Then find how many gallons of water the pigs need: 10 pigs * 4 gallons / pig = 40 gallons.

Then find how many gallons of water the ducks need: 20 ducks * 1 / 4 gallon / duck = 5 gallons.

Now add up all three quantities of water to find the total water needed: 5 gallons + 40 gallons + 30 gallons = 75 gallons.

Now divide the total water needed by Casey's pumping rate to find how long she spends pumping: 75 gallons / 3 gallons / minute = 25 minutes.

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The answer: 25