it is quite a simple sum, as you see: you could do it in a minute because you have been to a good school and have taken pains with your lessons; but it was quite otherwise with poor nigel. he sat down to work out his sum with a piece of chalk on a smooth stone. he tried it by practice and the unitary method, by multiplication, and by rule-of-three-and-three-quarters. he tried it by decimals and by compound interest. he tried it by square root and by cube root. he tried it by addition, simple and otherwise, and he tried it by mixed examples in vulgar fractions. but it was all of no use. then he tried to do the sum by algebra, by simple and by quadratic equations, by trigonometry, by logarithms, and by conic sections. but it would not do. he got an answer every time, it is true, but it was always a different one, and he could not feel sure which answer was right.