BECE Mathematics 2018 Paper

Volume of a cylinder $=\pi r^2 h$$\; \text{ Volume } \; = 20 \text{mcm}^3$$\; \text{ Height } \; = 5 \text{cm}$Substitute volume and height into the equation and solve for the value of $r$, radiu$20\pi = \pi \times r^2 \times 5$Divide both sides of the equation by $\pi \times 5$ to make $r$ the subject.$\; \frac{20\pi}{\pi \times 5} = \; \frac{\pi \times r^2 \times 5}{\pi \times 5}$$4 = r^2$Take square root of both sides or $r$ is a value when multiplied by itself will give 4 , which is $2$ because $2 \times 2 = 4$$2 = r$Thus$2 \times 2 = r^2$Every number is raised to the power 1$2^1 \times 2^1 = r^2$From the law of indices, $a^m \times a^n = a^{m+n}$ $\; 2^{1+1} = r^2$$\; 2^2 = r^2$Since the powers are the same, the bases are also the same$2 = r$