?$10,$??$12,$??$15$?的最小公倍數(shù)是?$60,$?
設(shè)木棍?$60$?厘米。
?$ 60\div 10 = 6($?厘米?$),$?
?$60\div 12 = 5($?厘米?$),$?
?$60\div 15 = 4($?厘米?$)。$?
?$ 10$?等份的為第一種刻度線,共?$10 - 1 = 9($?條?$);$?
?$ 12$?等份的為第二種刻度線,共?$12 - 1 = 11($?條?$);$?
?$ 15$?等份的為第三種刻度線,共?$15 - 1 = 14($?條?$)。$?
第一種與第二種刻度線重合的條數(shù):
?$6$?和?$5$?的最小公倍數(shù)是?$30,$?
?$60\div 30 - 1 = 2 - 1 = 1($?條?$);$?
第一種與第三種刻度線重合的條數(shù):
?$6$?和?$4$?的最小公倍數(shù)是?$12,$?
?$60\div 12 - 1 = 5 - 1 = 4($?條?$);$?
第二種與第三種刻度線重合的條數(shù):
?$5$?和?$4$?的最小公倍數(shù)是?$20,$?
?$60\div 20 - 1 = 3 - 1 = 2($?條?$);$?
三種刻度線重合的沒有,
?$6、$??$5$?和?$4$?的最小公倍數(shù)是?$60。$?
因此,共有刻度線?$9 + 11 + 14 - 1 - 4 - 2 = 27($?條?$),$?
?$ $?木棍總共被鋸成?$27 + 1 = 28($?段?$)。$?
答:木棍總共被鋸成?$28$?段。