Firstly, the rate of increase of Canton = 80/7720 = 0.010 The rate of increase of HP = 120/3200 = 0.0375 Apply the formula of compound interest==> A =A'(1+i)^n The population will be equal when the following equality is satisfied
7720(1+0.01)^n = 3200(1+0.0375)^n
or
7720x1.01^n = 3200x1.0375^n
Divide both sides by 3200 ===>(193/80)x1.01^n=1.0375^n
