H.C.F同L.C.M...20分

56=1,2,4,7,8,14,28,56
64=1,2,4,8,16,32,64
HCF=8
LCM=448


48=1,2,4,6,8,12,16,24,48
72=1,2,3,4,6,8,9,12,18,24,36,72
HCF=24
LCM=144


24,42,60
HCF=6
LCM=840


15,60,75
HCF=15
LCM=300

56= 2 x 2 x 2 x 7
64= 2 x 2 x 2 x 2 x 2 x 2
HCF= 2 x 2 x 2 = 8
LCM= 2 x 2 x 2 x 2 x 2 x 2 x 7 = 448

48= 2 x 2 x 2 x 2 x 3
72= 2 x 2 x 2 x 3 x 3
120= 2 x 2 x 2 x 3 x 5
HCF= 2 x 2 x 2 x 3 = 24
LCM= 2 x 2 x 2 x 2 x 3 x 3 x 5 = 720

24,42,60
24= 2 x 2 x 2 x 3
42= 2 x 3 x 7
60= 2 x 2 x 3 x 5
HCF= 2 x 3 = 6
LCM= 2 x 2 x 2 x 2 x 3 x 3 x 5 x 7 = 5040

15,60,75
15= 3 x 5
60= 2 x 2 x 3 x 5
75= 3 x 5 x 5
HCF= 3 x 5 = 15
LCM= 2 x 2 x 3 x 5 x 5 = 300

2008-07-16 15:13:19 補充：
24,42,60

LCM應該係
= 2 x 2 x 2 x 3 x 5 x 7 = 840

56=
64=
HCF= 8
LCM=448

48=
72=
120=
HCF=24
LCM=720

24,42,60
HCF=6
LCM=840

15,60,75
HCF=15
LCM= 300