How many gallons of water will it take to fill a round pool, 14 ft. in dia. and 48 inches high
Pi * r * r * d
3.14 * 7 * 7 * 4 = 615 cubic feet.
There are 7.48 gallons/cubic foot, so 615 * 7.48 = 4600 gallons
You can’t seriously expect us to accept ROUNDED NUMBERS! Think of the children!
Seriously though, the OP only specified 2 significant digits, so it would be wrong to provide more precision for the answer.
If the pool were specified as 14.00 ft in diameter and 48.00 inches high, the answer would be 4606 gallons.
615 cubic feet then.
(get it, now they’re cubed numbers)
He’s not going to be happy when he has to go back to the store to get 48 more bottles of water.
Or when he discovers that a few gallons evaporated while he went back to the store.
While your answer is correct, I have to nitpick your formula slightly. The volume of a cylinder is Pi * r * r * h, where h = height, which in this example would be the four feet. D would be the diameter, 14, which you correctly halved to give the radius.
i think his d = depth.
Or you might prefer something expressed a bit more naturally.
Maybe not… but I’ll bet he’s happy that we solved his homework problem for him 
Probably not
The problem does not give the number or total volume of children in the pool. Naturally, you should subtract the volume of their submerged portions from the final answer.
European or African children?
Insert hose, turn on, wait around…full? Turn off.
Empty pool into bottles, count bottles, put back in pool.
OK. That sounds reasonable. They are the same thing.
The pool is 48 inches high. You are planning on filling it right up to the rim? How about leaving a few inches at the top so the pool doesn’t overflow when the kids climb in?
Yes he does expect ROUNDED NUMBERS.
Read the OP, chacoguy! It’s a ROUND pool! 
That said, though, we have another problem:
Okay, then, how do you fill a ROUND pool with CUBES of water?
(Yes, yes, I’ve studied Calculus and I understand that you can fill the round pool with water cubes, to a closer and closer approximation, by using smaller and smaller water cubes. This is a simple application of Triple Integration. But in this problem, we’re specifically using FOOT CUBES, which can at best give us a ROUND result. There’s a 4-foot deep paradox in there somewhere.)
(ETA: Traditionally, the volume of kids would be ignored for problems like this, until you get into Differential Equations.)
Wait for them to melt?