A boy added all natural numbers from 1 to 10, however he added one number twice due to which the sum becomes 58. What is the number which he added twice?

Answer: Option A

Sum of natural number from 1 to 10
$$\begin{array}{rl}& =\frac{\left(n\right)\left(n+1\right)}{2}\left(\text{where }n=10\right)\\ & =\frac{10\times 11}{2}\\ & =55\end{array}$$
Clearly, we can see the number which is added twice = 58 - 55 = 3