CONSIDERING how many fools can calculate, it is surprising that it should be thought either a difﬁcult or a tedious task for any other fool to learn how to master the same tricks.

Some calculus-tricks are quite easy. Some are enormously difﬁcult. The fools who write the text— . books of advanced mathematics—and they are mostly clever fools—seldom take the trouble to show you how easy the easy calculations are. On the contrary, they seem to desire to impress you with their tremendous cleverness by going about it in the most diﬂicult way.

Being myself a remarkably stupid fellow, I have had to unteach myself the difﬁculties, and now beg to present to my fellow fools the parts that are not. hard. Master these thoroughly, and the rest wm follow. What one fool can do, another can.

CHAPTER I.

TO DELIVER YOU FROM THE PRELIMINARY TERRORS.

THE preliminary terror, which chokes oﬂ’ most ﬁfth- form boys from even attempting to learn how to calculate, can be abolished once for all by simply stating what is the meaning—in common-sense terms—of the two principal symbols that are used in calculating.

These dreadful symbols are: (1) d which merely means “a little bit of.”

Thus dm means a little bit of w; or du means a little bit of u. Ordinary mathematicians think it more polite to say“ an element of,” instead of “ a little bit of.” Just as you please. But you will ﬁnd that these little bits (or elements) may be considered to be indeﬁnitely small.

(2) I which is merely a long S, and may be called (if you like) “ the sum of.” Thus Ida: means the sum of all the h’ttle bits