Why all the calculators for android not working properly?

Bought a phone Lenovo A 760 on Android. Tried Google Play all the free calculators and not all work as usual. Example: enter 5 + 10 = and the calculator gives the result "15". If you now press the "=" sign again, then nothing will happen! And all desktop calculators, all calculators on older phones, iOS press equal sign repeats the last action. A lot and constantly think, ready to pay for the program-calculator for your phone, but not sure that will get the same garbage in the paid version, times all free so weird function. Does anyone know the "normal" calculator for Android?
October 3rd 19 at 01:42
3 answers
October 3rd 19 at 01:44
Not looking hard enough. Free and your requested functionality. There is also a paid version. Suggest.
RealCalc Scientific Calculator
Once I got it on sale. Also suggest this calculator! - Fanny_Bahring commented on October 3rd 19 at 01:47
October 3rd 19 at 01:46
Email the developers a few calculators - could someone fix.
October 3rd 19 at 01:48
Standard calculator in Samsung performs a repeat operations "="

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