Number theory · Digit sum · Decimal representation · Counting by listing
Lili noticed that the digits of the year \(2015\) have average \(2\), because \(\frac{2+0+1+5}{4} = 2\). How many years of the 21st century after \(2015\) have the same digit average as \(2015\)?
- A \(1\)
- B \(2\)
- C \(5\)
- D \(6\)
- E \(9\)
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Slovenian High School Mathematics Competition for Vega Awards (MaSSA), regijsko (regional) round 2015, 1. letnik, category A, problem A2. Organized by DMFA Slovenije (Society of Mathematicians, Physicists and Astronomers of Slovenia). Source