158518

We thought that if the candles last less than a year, then his parents would need to buy 66 candles overall. We got this answer by adding 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 together.

If the candles last more than a year, his parents would only need to buy 11 candles because they could reuse all the candles.