Elio makes candles that are 14cm. each candle burns 8 hours before going out. he is wondering how many hours a 21 cm tall candle can burn for. he assumes that the relationship between the height of a candle and number of hours it burns (h), is proportional.

Elio is right in assuming the relationship between the height and the hours it burns is proportional.

Find the unit rate

14 ÷ 8 = 1.75 cm/h

Divide

21 ÷ 1.75 = 12

You can set this up as an algebraic equation to check the answer.

If the candle is 21 cm tall, it will burn for 12 hours.

The diameter would be twice 5, or 10