What are the addition problems that go into 84?

Answer 1

There are infinitely many possible answers:

0 + 84, 1 + 83, 2 + 82, ...

Then consider numbers to 1 decimal place:

0.1 + 83.9, 0.2 + 83.8, 0.3 + 83.7, ...

and the 2 dp:

0.01 + 83.99, 0.02 + 83.98, 0.03 + 83.97, ...

then 3 dp, 4, dp,and so on.