Use the formula for the volume of a cylinder to work out how much wax you need to make one candle.
π×5²×15 = 375π
Then divide the amount of wax you have by the amount of wax you need to produce one candle to work out how many candles you can make.
4500 ÷ 375π = 3.82
However, you can't produce 82% of a candle, so you have to round down to 3 candles.
