Problem: Find the mass of a cylindrical cake with radius 5.5 cm and height 11 cm, given that each cubic centimetre has mass 0.4 g, and give the final answer to 1 d.p. 1. The volume of a cylinder is given by $V=\pi r^2 h$. 2. Substitute $r=5.5$ cm and $h=11$ cm to get $V=\pi(5.5)^2(11)$. 3. Compute $5.5^2=30.25$. Compute $30.25\times11=332.75$. 4. Therefore $V=332.75\pi\text{ cm}^{3}$. 5. The mass is density times volume, so $m=\rho V$ with $\rho=0.4\text{ g cm}^{-3}$. 6. Substitute $V=332.75\pi$ to get $m=0.4\times332.75\pi=133.1\pi\text{ g}$. 7. Evaluate numerically $m\approx133.1\times\pi\approx418.132\text{ g}$. 8. Rounding to 1 d.p. gives $m\approx418.1\text{ g}$. Final answer: $418.1\text{ g}$.