Duong owns a collection that has 169 coins and
he wishes to distribute these coins to his friends
such that no two friends receive the same number
of coins. At most how many friends can Duong
distribute these coins to?

As shown in the diagram,
the flowers are arranged fol-
lowing a pattern: the first
row has 1 flower, the second
row has 3 flowers, the third
row has 5 flowers, and the
forth row has 7 flowers. How
many flowers are there in the
25th row?