Originally Posted by

**ashleysmithd** Hi,

I've been learning how to use the power series for e^x, however I'm confused as to what level of 'accuracy' you are supposed to go to.

For instance, the question:

Determine the value of 5e^0.5, correct to 5 significant figures, by using the power series for e^x.

As I begin to multiply 0.5 by the power 2 and divide by the factorial 2, I add one to the power and factorial every time and this increases the accuracy of my answer. However there is no telling how accurate a question (like the one above) wants my answer to be. I could multiply 0.5 by the power of a billion and divide by the factorial of a billion if I wanted, theoretically I think it's infinite.

Am I missing some kind of rule here? Answering this question without knowing how accurate it needs to be seems impossible.

If someone can help me out here that would be great.

cheers.