Question:
A king wanted to reward his advisor, a wiseman of the kingdom. So, he asked the wiseman to name his own reward. The wiseman thanked
the king, but said that he would ask only for some gold coins each day for a month. The coins were to be counted out in a pattern of one
coin for the first day, 3 coins for the second day, 5 coins for the third day and so on for 30 days. Without making calculations, find how
many coins will the advisor get in that month?
Solution:
Let the advisor get $x$ coins in that month.
According to the question, advisor get coins upto 30 days as pattern
$1+3+5+\ldots$
Here, $n=30$
We know that, sum of first $n$ odd natural numbers $=n^{2}=(30)^{2}=30 \times 30=900$
Hence, the advisor get 800 -coins in that month.