Ravindra and Hongshu made a pizza together. Ravindra ate $\frac{2}{5}$ of the pizza. Hongshu ate half as much as Ravindra. What percentage of the original pizza was left?
(A) 20
(B) 30
(C) 40
(D) 50
(E) 60
Since Ravindra ate $\frac{2}{5}$ of the pizza and Hongshu ate half as much as Ravindra, then Hongshu ate $\frac{1}{2} \times \frac{2}{5}=\frac{1}{5}$ of the pizza.

After these two had eaten, there was $1-\frac{2}{5}-\frac{1}{5}=\frac{2}{5}$ of the pizza left.

As a percentage, $\frac{2}{5}$ is equivalent to $40 \%$, so there was $40 \%$ of the original pizza left.

ANSWER: (C)