I've read that 1 in 28 French soldiers and 1 in 32 British soldiers died over the course of the war, but many soldiers didn't enter into combat until later in the war. What were the chances of a British or French soldier who was at Mons or Charleroi surviving to the end of the war?
I really cannot say for the French soldiers, as there are so many factors at play, that I can't say with any degree of accuracy.
I don't know where you got 1 in 32 British soldiers dying. By contemporary sources, about 8.7 million British and commonwealth soldiers served in WW1, British statistics indicate that 956,000 British and commonwealth troops died, making for a death rate of approximately 1 in 9, or about 11%
In fact, if we just want to include troops from the British Isles, no commonwealth troops, they suffered worse than average. Of all troops from the British Isles (England, Wales, Scotland, Ireland), which numbered about 5.7 million, 705,000 died, making for a KIA rate of 12.355%, slightly less than 1 in 8. If you can show me where you found the 1 in 32 figure, I'd be thankful.
I'm sorry to disappoint, but I cannot answer your question for a few reasons.
First, the same units did not fight at every battle, and units were frequently rotated in and out of the front lines to avoid low morale or the destruction of units.
We would also have to assume that this person was unwounded, as if they were wounded, it would be a whole other number. Of those who were wounded, and survived, about 69% returned to duty, while the remainder were either employed in sedentary and non-frontline work or discharged, both of which clearly less dangerous than front line work.
I hope someone can give you an answer.