A test has 10 true/false questions. How many different tests can be turned in to the teacher?

The same as the greatest number that can be written with 10 binary bits:  1,024

Each question has 2 possible answers. There are 10 questions. 1 - 2 2 - 2 3  - 2 4 - 2 5 - 2 6 - 2 7 - 2 8 - 2 9 - 2 10 2                                                                                      There can be 20 different tests.