Mobile operating systems have bugs—we get it—but it's surprising that Apple is reportedly having some issues getting its Calculator app to work correctly in iOS 11. As reported by CNET, the app currently has issues registering your responses if you crunch your numbers too quickly.
"There appears to be some 'animation lag' at work: When you tap a number, it briefly lights up and then fades. But after the second number, if you try tapping a function (plus, minus, multiply, etc.) before the number has fully faded, it won't register," Rick Broida writes.
Apple doesn't appear to have a fix for the Calculator issues just yet—not even in the latest iOS 11.2 beta, which helps address the problem, but doesn't solve it completely. If you need a more accurate number-cruncher on your iOS 11 device, try going a little slower when tapping in your numbers to ensure your iPhone correctly registers your inputs.
You can also try using a third-party calendar app until Apple improves Calculator's accuracy. The Sweet Setup recommends PCalc ($10), but if you're just looking for a temporary fix for simple calculations, give the free PCalc Lite a try.