2005 PMWC Problems/Problem T6
Problem
\begin{eqnarray*} 1+2 &=& 3 \\ 4+5+6 &=& 7+8 \\ 9+10+11+12 &=& 13+14+15 (Error compiling LaTeX. Unknown error_msg)
If this pattern is continued, find the last number in the th row (e.g. the last number of the third row is ).
Solution
There are 3 numbers in the first row, 5 numbers in the second row, and numbers in the th row. Thus for the th row, the last number is
Since the sum of the first odd number is , the last number on the th row is .
See also
2005 PMWC (Problems) | ||
Preceded by Problem T5 |
Followed by Problem T7 | |
I: 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 • 11 • 12 • 13 • 14 • 15 T: 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9 • 10 |