Question

If we add first n numbers, we get ______

(a) \(\frac{n (n+1)}{2}\)

(b) n-1

(c) n^2

(d) n^2-1

The question was asked in my homework.

I want to ask this question from Patterns in Squares in chapter Squares and Square Roots of Mathematics – Class 8

Answer 1

Right option is (a) \(\frac{n (n+1)}{2}\)

Explanation: If we add first n numbers we get \(\frac{n (n+1)}{2}\). For example, if we add 1 + 2 + 3 + 4 + 5, we get 15.

Here, we added first 5 numbers. Here, \(\frac{n (n+1)}{2} = \frac{5 (5+1)}{2} \)= 15.

Hence, \(\frac{n (n+1)}{2}\) would be the correct answer and the other options would be incorrect.