There are 81 cars in the CMC parking lot, which are all Acuras, Beetles, or Camrys. There are half as many Acuras as Beetles. The number of Camrys is $80 \%$ of the number of Acuras and Beetles together. How many of the 81 cars are Beetles?
(A) 36
(B) 30
(C) 45
(D) 51
(E) 66

## Part C: Each correct answer is worth 8.
Let $B$ be the total number of Beetles in the parking lot.

Then the number of Acuras is $\frac{1}{2} B$.

Also, the number of Camrys is $80 \%$ of $\frac{1}{2} B+B$, so the number of Camrys is $\frac{4}{5} \times \frac{3}{2} B=\frac{6}{5} B$.

Therefore, since the total number of cars in the parking lot is 81 , then $B+\frac{1}{2} B+\frac{6}{5} B=81$ or $\frac{27}{10} B=81$, or $B=\frac{10}{27} \times 81=30$.

Therefore, the number of Beetles is 30 .

ANswer: (B)