Question

How can you use a quick picture to find 3x2.7

Answer 1

Tie should see right away that the answer should be 8.1

Answer 2

If you mean like a method to solve it fast here I have 1 solution I usually use;

3x2.7
3x.7=2.1
3x2=6
Then in the question there is 1 number behind the decimal point so the answer should have 1 number behind as well.
=8.1