It is a trifling error to call eight and four thirteen, but it
often may disconcert an immense calculation. Like the pebble in the
shoe, small in itself, it may do great injury. Some years ago there
traveled through the country a genuine "lightning calculator." You could
put down any number, big or little, while his back was turned, and he
would turn again and mark the total with far greater rapidity than he
could speak, and he thought out the total far quicker than he could mark
it. Of course, he had a magic book to sell, but when you came to read
his magic book and see how he did it, you found it was the same old way,
only he was more expert than you. He could add four thousand two hundred
and twenty eight and three thousand six hundred and fifty four as easily
as you could forty two and thirty six, or perhaps four and three, so you
see that the scheme of running up a single column of figures is at best
a clumsy one.
YOU EXPOSE YOURSELF
to additional errors by enlarging the possible additions in a body of
numbers. We are taught the multiplication table up to twelve times
twelve.
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