"A pound of butter at 1s.3d., half-a-pound of Is.4d. tea, a pound of cheese at 8d., and six eggs at 1s 3d. a dozen - if I give you 10s. how much change will I have?" Grocer (after writing it down): "6s. 9 1/2d." "Thanks-It's my home-work for to-night!"