Question

why we have use the formula k:1 when we ask to find ratio and derivation of that formula

Answer 1

$$\begin{gathered} \mathrm{In}\mathrm{section}\mathrm{formula}\mathrm{using}\mathrm{k}:1\mathrm{ratio}\mathrm{simplify}\mathrm{the}\mathrm{calculation}\mathrm{although}\mathrm{you}\mathrm{can}\mathrm{also}\mathrm{use}\mathrm{the}\mathrm{ratio} \\ \mathrm{a}:\mathrm{b}\mathrm{and}\mathrm{still}\mathrm{the}\mathrm{ratio}\mathrm{will}\mathrm{be}\mathrm{same}\mathrm{as}\mathrm{that}\mathrm{of}\mathrm{calculated}\mathrm{by}\mathrm{k}:1\mathrm{but}\mathrm{calculation}\mathrm{will}\mathrm{be}\mathrm{bit}\mathrm{lengthy}. \end{gathered}$$