Question

There are two candles of same length and same size. Both of them burn at uniform rate. The first one burns in 5 hr and the second one burns in 3 h. Both the candles are lit together. After how many minutes the length of the first candle is 3 times that of the other?

(a) 90

(b) 120

(c) 135

(d) 150

Answer 1

Answer is : (d) 150

We have, length and size of two candles are same. Let L be the length of candles.

Given, first candle burns in 5 h and second candle burns in 3 h.

In one hours length of candles are L/5 and L/3, respectively.

Let after time t h the length of candles are L₁ and L₂.

∴ L₁ = L - L/5 t and L₂ = L - L/3 t

According to the problem,