The first part of the Genius Quiz has 30 questions and the second part has 50 questions. Alberto answered exactly $70 \%$ of the 30 questions in the first part correctly. He answered exactly $40 \%$ of the 50 questions in the second part correctly. The percentage of all of the questions on the quiz that Alberto answered correctly is closest to
(A) 59
(B) 57
(C) 48
(D) 51
(E) 41
Alberto answered $70 \%$ of 30 questions correctly in the first part.

Thus, Alberto answered $\frac{70}{100} \times 30=21$ questions correctly in the first part.

Alberto answered $40 \%$ of 50 questions correctly in the second part.

Thus, Alberto answered $\frac{40}{100} \times 50=20$ questions correctly in the second part.

Overall, Alberto answered $21+20=41$ of $30+50=80$ questions correctly.

This represents a percentage of $\frac{41}{80} \times 100 \%=51.25 \%$.

Of the given choices, this is closest to $51 \%$.

ANSWER: (D)