# 1/3+1/5+1/7...............=2

• Jun 18th 2010, 03:18 AM
kingping
1/3+1/5+1/7...............=2
hi guy's

i need some help on making a formula for this 1/3+1/5+1/7...............=2
i need to be able to fill in any number e.g 1/3+1/5+1/7...............=45

thanks
kingping
• Jun 18th 2010, 03:56 AM
mr fantastic
Quote:

Originally Posted by kingping
hi guy's

i need some help on making a formula for this 1/3+1/5+1/7...............=2
i need to be able to fill in any number e.g 1/3+1/5+1/7...............=45

thanks
kingping

There is no formula for the exact sum of the first n terms of this particular series (called a harmonic series). Your best bet is to write a simple program to sum the terms and to terminate after reaching the required sum. The output would be how many terms were summed.
• Jun 18th 2010, 04:25 AM
Bacterius
And note that usually the sum of the harmonic series will not be an integer. So you should allow input for real numbers :)
• Jun 18th 2010, 05:44 AM
ebaines
Quote:

Originally Posted by Bacterius
And note that usually the sum of the harmonic series will not be an integer. So you should allow input for real numbers :)

Yes - in fact, the sum of the first N terms of this series can never be an integer.
• Jun 18th 2010, 05:46 AM
Bacterius
Quote:

Yes - in fact, the sum of the first N terms of this series can never be an integer.
Where is that thanks button ?!
Thanks for the precision though Ebaines, I would have thanked your post in normal circumstances :(