Question

without adding find the sum 1+3+5+7+9+11+13+15+17

Answer 1

first count the number of numbers
there are nine numbers-1,3,5,7,9,11,13,15,17
now since they are all odd the sum is the square of the total no of numbers
that means the sum is 9 power 2which is 81
this only works for consecutive odd numbers

Answer 2

Given,

The series: 1+3+5+7+9+11+13+15+17

To find,

The sum of all the terms of the series.

Solution,

We can easily solve this problem by following the given steps.

According to the question,

We have the following series:

1+3+5+7+9+11+13+15+17

This series has consecutive odd numbers (Odd numbers are the numbers that can not be divided by 2. For example, 1 and 3 are odd numbers).

We know that the following formula is used to find the sum of consecutive odd numbers:

Sum = n² where n is the number of the total terms.

In this case, we have n = 9.

So,

S9 = (9)²

S9 = (9×9)

S9 = 81

Hence, the sum of 1+3+5+7+9+11+13+15+17 is 81.