Two candles have the same length but they are made of different materials. One of these candles burn completely in 3 hours and the other burn completely in 4 hour. Both of the candles burn in a uniform rate.

At what time should I lit both candles if I want that the length of one candle be twice the length of the other candle exactly at 4:00 pm?

Guest Jan 5, 2020

#1**+2 **

rate x time = distance (or amount burned away)

1 candle / 3hr = 1/3 candle/ hr for rate of the fast burner the other is 1/4 candle/hr

The amount of candle remaining after some time t is 1 candle - rate* t

The slower burner will be twice as long as the faster burner at what point?

1 - 1/4 candle/ hr x t = (1 - 1/3 candle/hr x t) x 2 solve for t

1-1/4 t = 2 - 2/3 t

-3/12 t = 1 - 8/12 t

5/12 t = 1

t = 12/5 = 2.4 hours start 2.4 hours before 4 pm or 1:36 PM

ElectricPavlov Jan 5, 2020