Question

Elio makes candles that are 14 cm tall. 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. How long can a 21 cm tall candle burn for?

Answer 1

(burn time)/(8 h) = (21 cm)/(14 cm)
burn time = (8 h)*(21/14)
burn time = 12 h

Elio expects the 21 cm candle to burn 12 hours.

Answer 2

14cm can burn 8 hours
21cm can burn x hours

14x=8x21
14x=168
x=12

A: 21cm tall candle can burn for 12 hours.

Hope this helps.