Respuesta :

Answer:

Step-by-step explanation:

The first diagram and second diagram both shows 1 + 2 + 3 + 4

The third diagram shows :

First diagram + second diagram = 4 squares row x 5 squares column

First diagram = second diagram

So, 2 times first diagram = third diagram

2 x (1+2+3+4) = 4 x 5

1+2+3+4 = [tex]\frac{4x5}{2}[/tex]