The calculator in iOS 11.1 isn’t working. If you enter a simple equation, like 1 + 2 + 3, it doesn’t give 6 as the answer.
Instead, it shows 24.
The app isn’t registering the “+” sign fast enough. It does work if you type very slowly.
Since you can’t totally rely on the calculator app right now, there are a few things you can use instead. You can either use the search bar or Google. You can even use a calculator app from the app store.
Hopefully, Apple will issue an update soon. Until then, be wary of answers the calculator gives.