Question

Without adding find the sum.
1+3+5+7+9+11+13+15+17+19​

Answer 1

Answer:

1+3+5+7+9+11+13+15+17+19 = 102 = 10×10 =100. So, 100 is the solution for the question number (ii).

Answer 2

Heya!

This question has a very simple logic.

1 + 19 = 20,

3 + 17 = 20,

5 + 15 = 20, and so on.

In total, we see that we can make 5 total pairs which have a sum of 20.

So the answer to the question is 5 x 20 = 100.

100 can also be written as 10 x 10, and as we can see, there are a total of 10 terms in this expression.

So for all these questions, the simple formula is $n^2$ where n is the number of terms.

Answer: 100

I hope this helps. :)