Convert decigram to troy pennyweight

Gold, silver and platinum are priced per troy ounce, 31.103 g, which is about 10 % heavier than the ordinary (avoirdupois) ounce of 28.35 g. Twelve troy ounces make a troy pound of 373 g, 20 pennyweights make an ounce, and the grain, 64.8 mg, is the one unit the two systems share; it also survives in the weights of bullets and, in the US, of old-fashioned medicine doses (5 grains of aspirin is 324 mg). A standard 400 oz 'good delivery' gold bar weighs 12.4 kg.

Recipes give ingredients either by volume (millilitres, cups, spoons) or by weight (grams, ounces), and the two cannot be converted directly: the weight of a given volume depends on the ingredient. A cup of water weighs about 240 g, a cup of flour only about 125 g and a cup of sugar about 200 g. The link between the two is the density of the ingredient.