Things aren't adding up as the iOS 11 calculator is giving the wrong answers37
Check out the bug yourself by adding the following numbers, 1+2+3. Hit the equal sign and you should get 6 as the answer. But if you enter the numbers too quickly, you just might come up with the incorrect answer of 24. The reason why this happens has to do with the animations used by the calculator. When you input a number by pressing on a button in the calculator app, the button lights up to confirm that you pressed the correct number. But an input won't register unless the previous animation is completed. Thus, if you are tapping in numbers too fast, certain key presses won't register.
Apple already knows about the bug. Company employee Chris Espinoza said in a tweet that there have been more than 70 complaints about the iOS 11 calculator issue. Eventually, we would expect Apple to fix the problem. Until it does, you can use the calculator app by entering numbers slowly. Or, you can head to the App Store and pick up a third party calculator for your iOS device.