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Francophone Mathematical Olympiad
2021 Francophone Mathematical Olympiad
1
R < 1/15 < S, R=/2 x 3/4 x 5/6 x ...x 223/ 224
R < 1/15 < S, R=/2 x 3/4 x 5/6 x ...x 223/ 224
Source: 2021 Francophone MO Juniors p1
April 3, 2021
algebra
inequalities
Francophone
Problem Statement
Let
R
R
R
and
S
S
S
be the numbers defined by
R
=
1
2
×
3
4
×
5
6
×
⋯
×
223
224
and
S
=
2
3
×
4
5
×
6
7
×
⋯
×
224
225
.
R = \dfrac{1}{2} \times \dfrac{3}{4} \times \dfrac{5}{6} \times \cdots \times \dfrac{223}{224} \text{ and } S = \dfrac{2}{3} \times \dfrac{4}{5} \times \dfrac{6}{7} \times \cdots \times \dfrac{224}{225}.
R
=
2
1
×
4
3
×
6
5
×
⋯
×
224
223
and
S
=
3
2
×
5
4
×
7
6
×
⋯
×
225
224
.
Prove that
R
<
1
15
<
S
R < \dfrac{1}{15} < S
R
<
15
1
<
S
.
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