Look at this diagram which shows two and one fifth of a rectangle shaded.
That's 2 whole rectangles and one fifth of a rectangle.
Let's multiply two and one fifth by 3.
This will give 3 lots of two and one fifth.
2 | 1 | + | 2 | 1 | + | 2 | 1 | = | 6 | 3 |
5 | 5 | 5 | 5 |
This gives 6 wholes and three-fifths shaded as shown.
So
3 | × | 2 | 1 | = | 6 | 3 |
5 | 5 |