Henry Ernest Dudeney/Puzzles and Curious Problems/10 - Mental Arithmetic

by : $10$

 * Mental Arithmetic
 * If a tobacconist offers a cigar at $7 \tfrac 3 4 \oldpence$,
 * but says we can have the box of $100$ for $65 \shillings$,
 * shall we save much by buying the box?
 * In other words, what would $100$ at $7 \tfrac 3 4 \oldpence$ cost?


 * By a little rule that we shall give the calculation takes only a few moments.