I have a Canon HS-1200TS calculator.
I do the following:
The low number is 47 and the high is 120 which is 73 difference.
Take the amount of increase which is 73 and then divide by the low number of 47
That is 1.55 x 100 and you get 155% increase.
My Canon HS-1200TS calculator shows 155.3100
On my Samsung S10 I have an free app called CalculatorPlus that shows:
155.319148936
Which of the 3 is the correct answer?
73 divided by 47 is not 1.55. It’s 1.5531914893617021276595744680851....
The problem you describe is a likely a function of the precision of the display or even of the calculator itself, not of the calculation. Calculators have a limit on precision as well as a limit on the display. Most all have enough precision to be irrelevant, but not always.