# You have two candles of equal length. Candle A takes six hours to burn, and candle B takes three hours to burn. If you light them at the same time, how long will it be before candle A is twice as long as Candle B? Both candles burn st a constant rate.

##### 1 Answer

Two hours

#### Explanation:

Start by using letters to represent the unknown quantities,

Let burn time =

Let initial length

Let length of candle A =

Writing equations for what we know about them:

What we are told:

At the start (when

At

so burn rate of candle A

=

At

so burn rate of candle B =

Write eqns for

e.g.

Check that at

Think about what we are asked for: Value of

Using eqns (1) and (2) above if

expand and simplify this