What is the height of a candle after 15 hours?

Question

Suppose that the height of the candle after 15 hours is 17.5 centimeters. What will be the height of the candle after 21 hours?

Please help!

Answer 1

h = mx + b

17.5 = m15 + b

So, you have two unknowns: m, which is the slope or rate of burn, and, b, which is the original height of the candle before burning. Since you have two unknowns, you need two equations. You have only one. Is this the full text of the problem?

If the b, or original height of the candle was 20, then the candle burned 3.5 cm in 15 hours, but, if it was originally 30, then, it burned 13.5 in 15 hours...