Problems from Greatest common divisor and Least common multiple

Find the greatest common divisor of the following sets of numbers: (34,25),(80,45),(66,52,70).

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Development:

34=2×17,    25=52

g.c.d.(34,25)=1 (They do not have common divisors but 1.)

80=24×5,    45=32×5

g.c.d(80,45)=5

66=2×3×11,    52=22×13,    70=2×5×6

g.c.d.(66,52,70)=2

Solution:

g.c.d.(34,25)=1g.c.d.(80,45)=5g.c.d.(66,52,70)=2

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Find the least common multiple of the following sets of numbers: (49,33),(56,100,24),(72,41,16).

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Development:

49=72,    33=3×11

l.c.m.(49,33)=3×72×11=1617

56=23×7,    100=22×52,    24=23×3

l.c.m.(56,100,24)=23×3×52×7=4200

72=23×32,    41=41×1,    16=24

l.c.m.(72,41,16)=24×32×41=5904

Solution:

l.c.m.(49,39)=1617l.c.m.(56,100,24)=4200l.c.m.(72,41,16)=5904

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