HOW TO SUM OF ALL ODD NUMBERS

Trick : just follow the rule that n X n = result, square the quantity of numbers in the series.

Example: 1) Calculate the sum of all ODD numbers in the group 1 to 90

Count the total ODD numbers in 1 to 90, i.e = 45
Multiply 45 X 45 = 2025

So the sum of all ODD numbers in the group 1 to 90 is  2025

Example: 2) Find the sum of all ODD numbers in the group 1 to 30

Count the total ODD numbers in 1 to 30, i.e = 15
Multiply 15 X 15 = 225

So the sum of all ODD numbers in the group 1 to 30 is  225