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National and Regional Contests
Moldova Contests
Moldova Team Selection Test
1999 Moldova Team Selection Test
1
1
Part of
1999 Moldova Team Selection Test
Problems
(1)
$\frac{1}{[a,b]} + \frac{1}{[b,c]} + \frac{1}{[c,d]} + \frac{1}{[d,e]}$
Source: Moldova TST 1999
8/7/2023
Let
a
,
b
,
c
,
d
,
e
a, b, c, d, e
a
,
b
,
c
,
d
,
e
(
a
<
b
<
c
<
d
<
e
)
(a < b < c < d < e)
(
a
<
b
<
c
<
d
<
e
)
be positive integers. FInd the greatest possible value of the expression
1
[
a
,
b
]
+
1
[
b
,
c
]
+
1
[
c
,
d
]
+
1
[
d
,
e
]
\frac{1}{[a,b]} + \frac{1}{[b,c]} + \frac{1}{[c,d]} + \frac{1}{[d,e]}
[
a
,
b
]
1
+
[
b
,
c
]
1
+
[
c
,
d
]
1
+
[
d
,
e
]
1
, where
[
x
,
y
]
[x,y]
[
x
,
y
]
denotes the least common multiple of
x
x{}
x
and
y
y{}
y
.
number theory