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I add to David C's comments with some additional context about the level of education that was common in the British environment at the time.  My guess is that it was similar in many other countries.

In (or about) 1849 one of my great-great grandfathers joined the Royal Sappers and Miners (the enlisted branch of the Royal Engineers and later merged into the Royal Engineers).  In order to join, he had to (a) have skills in a relevant trade and (b) be literate.  For this he got more money, but had to make a commitment to twelve years of service.

In (or about) 1845 another ancestor, this one a GGG grandfather, signed up for the 65th Regiment of Foot.  There was no requirement for him to be literate.  His pay was less than the Sappers and Miners of equivalent rank, but he only had to commit to eight years of service.

These two examples speak to the nature of education (or lack thereof) available to the working classes and those with a trade in early Victorian Britain.  Prior to 1833 there was no government involvement in education.  It wasn't until the mid 1840s that education started to be somewhat consistently available to those who could not afford private tuition or did not have access to a charity school.  In 1820 the literacy rate was only 53% and was strongly biased in favor of males.  But by 1870 it was 70%.  (The sources of data differ depending what you read, so these data points are representative and indicative of the improvement over 50 years.)  That GG grandfather probably learned his 3-rs (reading, 'riting and 'rithemtic) from a church-run charity school we know existed in his village during his childhood, and from his parents (his father was also literate).

Throughout this era few (aside from those with money) would get more than an elementary education.  So mathematics skills were rudimentary at best. To some extent, education continued on the job.  In Britain, the Corp of Army Schoolmasters was formed in 1846.  Many enlisted men also learned from the senior non-commissioned officers.  A similar process would have worked at sea, both in commerce and in the navy.  I suspect my GGG grandfather was illiterate (or close to it) when he joined the 65th, but when he took his retirement, sometime between  8 - 10 years of service, he was a colour sergeant, a rank he would not have achieved without some level of literacy.

Murray