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Saint Petersburg Mathematical Olympiad
2011 Saint Petersburg Mathematical Olympiad
2
GCD and LCM
GCD and LCM
Source: St Petersburg Olympiad 2011, Grade 9, P2
September 15, 2017
number theory
greatest common divisor
least common multiple
Problem Statement
a
,
b
a,b
a
,
b
are naturals and
a
×
G
C
D
(
a
,
b
)
+
b
×
L
C
M
(
a
,
b
)
<
2.5
a
b
a \times GCD(a,b)+b \times LCM(a,b)<2.5 ab
a
×
GC
D
(
a
,
b
)
+
b
×
L
CM
(
a
,
b
)
<
2.5
ab
. Prove that
b
∣
a
b|a
b
∣
a
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