How can a square root be a solution?

Question

I am seriously sturggling right now. My professor asked for an exact number, the square root was involved in the answer.

The question was: What is the (square root of) 28.

The answer was: 2 times the (square root) of 7. Instead, I put the decimal out to 15 decimal places, to be realistically exact.

In fact, the answer should have been my decimals because I believe leaving the square root was basically leaving the question unanswered. Involving a mathematical equation - square roots, division, multiplication, subtraction - would still be a question, and not an answer. An answer should be composed of whole numbers - 1, 2, 3 - and decimals - 1.5, 2.3333, 4.8763895, etc. Leaving a mathematical equation such as the square root would not be a true answer, especially since the question asked for an answer of a square root. Am I wrong?

Answer 1

The answer of 2 times square root of 7 is correct. It is an exact answer. Since the square root of 7 is an irrational number, the final answer cannot be expressed exactly using decimals.