Balti Tee 2018 · Ülesanne 2
Algebra
A table is given. For each , the -th row of the table contains the numbers in increasing order (from left to right) but not necessarily in consecutive cells; the remaining cells are filled with zeroes. Prove that there exist two columns such that the sum of the numbers in one of the columns is at least 19 times as large as the sum of the numbers in the other column.
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Ülevaade
Teemad
Jadad ja rekurrentsid
Lahendused
Lahendus
Observe that the sum of numbers in the first column is at most , the sum in the first and second columns is at most , the sum in the first, second and third columns is at most , etc. But the sum of all nonzero numbers equals , therefore the sum in the columns from -th to -th is at least
Therefore one of these columns has a sum at least . Therefore the ratio of sums in this column and in the first one is more than .
Võistluse kontekst
Balti Tee tulemused 2018
11 võistkonda
- Keskmine tulemus
- 4,3 / 5
- 4 või 5 punkti
- 9 / 11
- Eesti
- 5 / 5
Punktijaotus
Kõigi võistkondade punktid
| Võistkond | Punktid |
|---|---|
| Germany | 5 / 5 |
| St. Petersburg | 5 / 5 |
| Denmark | 5 / 5 |
| Estonia | 5 / 5 |
| Sweden | 2 / 5 |
| Norway | 5 / 5 |
| Lithuania | 5 / 5 |
| Finland | 5 / 5 |
| Latvia | 5 / 5 |
| Poland | 5 / 5 |
| Iceland | 0 / 5 |