Marking Calculator, by Kwiius, is designed for teachers, with the sole purpose of making marking easier.

It allows you to enter a total for a test, then type one or more scores which are totalled and turned into a percentage on the fly.

Example:

A test is out of 40.
There three sections worth 10, 15 and 15.
Student A gets 8, 13 and 11.
Student B gets 5.5, 10 and 9.5.
Another test is a single mark out of 17.
Student C gets 12.

When you open Marking Calculator, type 40, then Go or Done.
Type 8 + 13 + 11. The screen displays 32/40 and 80%.
Press the # key. The input box clears and the screen displays 0/40 and 0%.
Now type 5*5 + 10 + 9*5. The screen displays 25/40 and 62.5%.
Press the pause key. The input box clears and returns to the initial screen.
Type 17 then Go or Done.
Type 12. The screen displays 12/17 and 70.6%.