Very tricky - I got to 4090 added the last 10 and got 5000?:|


Welcome back bump. So you got 5000, right?      Just kidding. 🙂


 


When adding there can be a tendency to round the last of the smaller figures to 1000 rather than 100. A play on the mind if you don't concentrate.



 


I came first in maths every year in high school so maybe that is why I can't see the trick.