[Math] Prove that $\sum {{a_n}} $ converges iff the sequence of partial sums is bounded where $a_n\geq 0$

Question

Let (${a_n}$) be a sequence of nonnegative real numbers. Prove that $\sum {{a_n}} $ converges iff the sequence of partial sums is bounded.

Uh I don't know how to do this proof. Please help!

Answer 1

Assuming you mean nonnegative sequence of real numbers (it is very false otherwise), here's a hint: Increasing sequences bounded above converge...