[Heinemann FP3 Chapter 5A Question 17]

Air you made a mistake in posting the question.

It should be

Okay i did the question once, got the correct answer but made a mistake in my working.

Initially i made the mistake of doing

then subsituting the values into the equation. solved the quad and got 2.222.

did you notice the error though ?

Here is my solution, not guarantee that is is correct.

then sub the values

giving

which disagrees with everybody.