Question Number 169538 by BRR last updated on 02/May/22
Commented by Tinku Tara last updated on 02/May/22
$$\mathrm{fare}\:\mathrm{increase}\:\mathrm{5}{x} \\ $$$$\mathrm{total}\:\mathrm{earning}\:=\left(\mathrm{400}−\mathrm{10}{x}\right)×\left(\mathrm{50}+\mathrm{5}{x}\right) \\ $$$${f}\left({x}\right)=\mathrm{20000}+\mathrm{1500}{x}−\mathrm{50}{x}^{\mathrm{2}} \\ $$$${f}\:'\left({x}\right)=\mathrm{1500}−\mathrm{100}{x} \\ $$$${x}=\mathrm{15} \\ $$$${max}\:{fare}=\mathrm{50}+\mathrm{15}×\mathrm{5}=\mathrm{125} \\ $$