Even then a miracle intervened to save him.

Arthur's Euclid was hopeless.

He hated the whole business of squares and angles and parallelograms with such intensity that it made him mentally and morally sick.

To his, as to some other minds, it was utter nonsense devised by a semi-lunatic for the bewilderment of mankind, and adopted by other lunatics as an appropriate form of torture of the young.
At length, in despair, Godfrey, knowing that Arthur had an excellent memory, only the night before the examination, made him learn a couple of propositions selected out of the books which were to be studied, quite at hazard, with injunctions that no matter what other propositions were set he should write out these two, pretending that he had mistaken the question.

This Arthur did with perfect accuracy, and by the greatest of good luck one of the two propositions was actually that which he was asked to set down, while the other was allowed to pass as an error.
So he bumped through somehow, and in the end the Indian Army gained a most excellent officer.