The trapezium is drawn on a centimetre grid

21 cm²

Step-by-step explanation:

Applying,

A = (a+b)h/2 Equation 1

Where A = area of the trapezium, a = length of the first parallel side, b = length of the second parallel side, h = height.

From the diagram

Given: a = 5 cm (5 grids), b = 9 cm (9 grids), h = 3 cm (3 grids)

Substitute these values into equation 1

A = 3(5+9)/2

A = 3(14)/2

A = 3×7

A = 21 cm²

step-by-step explanation:

hans did not square the 40-unit side; he merely multiplied it by 2.   incorrect.