A1. Riba has a $9 \mathrm{~cm}$ long head. Her tail is as long as the head and half the body together. The body is as long as the head and tail together. How long is the fish?
(A) $27 \mathrm{~cm}$
(B) $54 \mathrm{~cm}$
(C) $63 \mathrm{~cm}$
(D) $72 \mathrm{~cm}$
(E) $81 \mathrm{~cm}$
A1. If the tail of the fish is as long as the head and half the body combined, and the body is as long as the head and tail combined, then the body is as long as 2 heads and half the body combined. Therefore, half the body is 2 heads longer, which is $18 \mathrm{~cm}$. The body is $2 \cdot 18=36 \mathrm{~cm}$ long, and the tail is $9+18=27 \mathrm{~cm}$. The fish is $9+36+27=72 \mathrm{~cm}$ long.