1.甲数是50,乙数是40,甲数是乙数的百分之几?50÷40×100% = 125%2.甲数比乙数多百分之20,乙数是甲数的百分之几?甲数比乙多百分之几?1÷(1+20%)×100% = 5/6×100% ≈ 83.33%,乙数是甲数的百分之83.33%；(1+20%)÷1×...