5 1/2 x 1 x 2 1/2
\(5\dfrac{1}{2}\times 1 \times 2\dfrac{1}{2}\\ =\dfrac{11}{2}\times 1 \times \dfrac{5}{2}\\ =\dfrac{11\times 1 \times 5}{2\times 2}\\ =\dfrac{55}{4}\\ =13.75\)