數學:分數

(1)
(3又7/8) - (17/18) - (5/12)
= (31/8) - (17/18) - (5/12)
= (279/72) - (68/72) - (30/72)
= (279 - 68 - 30)/72
= 181/72
= 2又37/72


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(2)
(3又2/7) + (4/15) + (3又9/10)
= 3 + (2/7) + (4/15) + 3 + (9/10)
= 6 + (60/210) + (56/210) + (189/210)
= 6 + [(60 + 56 + 189)/210]
= 6 + (305/210)
= 6 + (61/42)
= 6 + (1又19/42)
= 7又19/42


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(3)
(7又5/12) + (13/15) + (1/18)
= 7 + (5/12) + (13/15) + (1/18)
= 7 + (75/180) + (156/180) + (10/180)
= 7 + [(75 + 156 + 10)/180]
= 7 + (241/180)
= 7 + (1又61/80)
= 8又61/80


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(4)
(6又7/24) + (5又1/18) + (5/6)
= 6 + (7/24) + 5 + (1/18) + (5/6)
= 11 + (21/72) + (4/72) + (60/72)
= 11 + [(21 + 4 + 60)/72]
= 11 + (85/72)
= 11 + (1又13/72)
= 12又13/72

都是先通分後分子做加減法，最後約分
(1)3又8分之7-18分之17-12分之5=181/72
(2)3又7分之2+15分之4+3又10分之9=313/42
(3)7又12分之5+15分之13+18分之1=1501/180
(4)6又24分之7+5又18分之1+6分之5 =877/72