sentence: examples digits digit can be memorized by their shapes , so that : 0 - looks like an egg , or a ball ; 1 - a pencil , or a candle ; 2 - a duck , or a swan ; 3 - an ear ; a pair of pouted lips 4 - a sail , a yacht ; 5 - a key ; 6 - a comet ; 7 - a knee ; 8 - a snowman , or a pair of glasses ; 9 - an apostrophe , or comma .