Lost in Addition

Number Theory Level 1

Find the number between 1 and 49 (inclusive) such that the sum to the left of it is equal to the sum to the right of it.

Note: For example, between 1 and 8, 6 would be the answer, as the sum of the numbers to the left of 6, which is $1+2+3+4+5=15,$ is equal to the sum of the numbers to the right of 6, which is $7+8=15.$

Bonus: Generalize it for any set of numbers from $k$ to $n$ with proof.