Abraham's mathematics exam had 30 algebra questions and 50 geometry questions, each worth 1 mark. He got $70 \%$ of the algebra questions correct, and his overall exam mark was $80 \%$. How many geometry questions did he answer correctly?
(A) 43
(B) 45
(C) 39
(D) 41
(E) 35
Abraham's exam had a total of 80 questions. Since he received a mark of $80 \%$, he got

$\frac{80}{100} \times 80=\frac{8}{10} \times 80=64$ questions correct.

We also know that Abraham answered $70 \%$ of the 30 algebra questions correctly, or a total of 21 questions.

This tells us that he answered 43 of the geometry questions correctly.

ANsWer: (A)