Calculation method of the collocation of two hats, three clothes and three pants in the third grade of mathematics;

1, each coat and three pairs of trousers have 1×3=3 collocation methods, and three coats and three pairs of trousers have 3×3=9 collocation methods.

2. Each hat, three coats and three pairs of trousers have 1×3×3=9 collocation methods.

3. Two hats, three coats and three pairs of trousers have a collocation method of 2×3×3= 18.