However if your talking pure math than its £2.7 to 2 sigfig, as the quantities in the question only has 2 significant numbers (sigfig) so you cant be sure that its not £27.01 of 10.01% and the counter was'nt accurate enough to count to 1 decimil point.
It's £2.70. There's a very easy rule. Remember that 10 percent is one tenth, 20 percent is 2 tenths, 30 percent is 3 tenths, 40 percent is ...you've guessed it, 4 tenths, and so on ..... right up to 90 percent being 9 tenths.
Now you know that you have to find one tenth of £27, and to find one tenth of anything, you divide by 10, just as you divide by 5 to find one fifth, by 3 to find one third, by 4 to find one quarter and so on.
Now, the easiest way to divide anything by 10 is simply to remove a zero from the end, and if there are no zeros, then to move the decimal point one place to the left. There are no zeros, and while it looks as if there are no points, the point is there, after the 7 - you just can't see it. But it is really 27.00, so move the point along one space and you get 2.70. Simple.