What is the formula for calculating the lifetime of a star?

[Johnboy]

Homework Statement

I have to calculate the lifetime of a star that is 300,000 times as luminous as the sun and 24 solar masses.

Homework Equations

lifetime = k * m/l

The Attempt at a Solution

lifetime = 10^10 * (24/300000)
lifetime = 800000 years


I feel as if this is almost too easy and am wondering if I have made an error along the way. In addition, I found this equation on the internet and don't really understand how it works despite knowing (or thinking I know) how to use it. I was hoping someone could explain it to me and if I am wrong, someone could point me in the right direction.

Many Thanks

John

 

[phyzguy]

1)The lifetime of the sun is about 10 billion years - this is the 10^10 in your equation.
2) A star with 24 solar masses has 24 times as much fuel as the sun.
3) A star 300,000 times as luminous as the sun is burning its fuel 300,000 times faster than the sun.

This gives the equation in your post. Does this answer it?