Worldwide, how many people die yearly from starvation?  How many of
these deaths could have been prevented by financial gifts to charities
from those in wealthy nations?

I have found on the internet numbers of worldwide yearly deaths from
starvation from 4 million to 16 million, but none of these sites said
how that number was arrived at or the source of the information.  The
best answer to my question would include reliable data from trusted
sources and some information on how that number was reached.

The simple answer to starvation would seem to be buying food.  But
there are obstructions that keep food from making it to many of those
in need - wars, corrupt governments, etc.  How much of the worldwide
deaths from starvation that are taking place could have been prevented
if those of us in wealthy nations opened up our pocketbooks?  Please
also provide how this answer is reached, and sources used.

Thanks in advance.

No sources. But, in the 70's, I took an elective course at the
community college near me. It was called Biosocial issues.  We
discusses among other things the starvation at that time in Africa. 
The instructors did not try to force any opinions on us, just tried to
get us to form our own. And, we certainly did that.

One question we researched was:  If we send food to those in Africa
who cannot get it for themselves, thus saving their lives, will they
then produce large numbers of children, and in the next drought thus
even more people will die from starvation?

We really debated this question, and frankly the class was sharply
divided.  Most did admit that probably this was true, but some felt
that one must do today what one can, and not worry about the future.
Others felt that since feeding them now meant more deaths in the
future, they did not wish to help.

A harsh reality. Whatever you decide to do, at least be aware of the
issues involved. And, do realize that the problems in Africa are much
greater today than 35 years ago, though today it is more dying of AIDS
than of starvation.

I am reminded of the organizations dedicated to buying slaves in
Africa (I mean this century, not 200 years ago) and freeing them.  It
has been proved that people kidnap others so they can "sell" them to
those "benevolent" organizations at very high prices.

If you want something to read then Peter Singer's 'Practical Ethics'
(2nd edition, cambridge University Press) has a useful chapter 8 on
'Rich and Poor'.
He discusses the idea of demographic transition (which is the fancy
word for what irlandes-ga is describing). There is a case for saying
that children are an asset in undeveloped countries: they can work at
an early age and, provided that they survive, will support their
parents when the parents grow old.  So people have large families.
When there is increased wealth there is demographic transition. The
poorer people still breed a lot.  Eventually,  things change. children
are educated, and so no longer part of the workforce. There is
provision for the elderly, so they no longer need children as
insurance. Women get more access to education and, later, more
satisfying jobs. They also acquire more control over their own bodies
and can choose whether to have a large family or not. When people feel
more secure then they choose smaller families. You can see this
transition in Britain, continental Europe and the USA. Our
great-grandparents  came from large families. We, typically, don't
choose to have a huge number of children. These developed states went
through the transition over a century ago. But many developing
countries are going through it now. So, feeding members of a poor
state may lead to a population explosion in the short term. But things
will even out as the state develops. Some european countries are now
failing to reproduce their current population levels.

You suggest "opening our pocketbooks", but one of the serious problems
for some poor countries is that the EU and USA protect their own
agricultural industries, making it impossible for third world
countries to export, while dumping surplus products on the world
market in competition of the poor countries.

One could also look at what has happened to the billions that have
already been lent to poor nations  - and the debt periodically
forgiven -  and ask what effect this has had, also ask by what means
additional funds could better be used.