Problem of the Week for Algebra and Up

Question: 

Will has four boxes of candels. One box is full, and each consecutive box has one fewer candle than the last. If Will has 450 candles in total, how many are in the full box? 

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Answer: The full box contains 114 candles.

Solution: The number of candles in the boxes will be four numbers whose average is 450 ÷ 4 = 112.5. Since the numbers are each one apart, we can reason that they are the two whole numbers before and after 112.5. So, there are 111, 112, 113, and 114 candles in the boxes. The full box therefore has 114 candles.