Harriet has a square piece of paper she folds it in half to form a rectangle and then folds it in half again the perimeter of the second rectangle is 30cm

area of the original square = 144 cm²

Step-by-step explanation:

You didn't include the whole question, but nonetheless this is the answer.

Take care. (:

check the picture below.

well, the angle at the vertex d is clearly not a right-angle, let's check for the one at the vertex f which does look like,   however if it's indeed, that means ef is perpendicular to df, in which case their slopes will be negative reciprocal of each other.

so the negative reciprocal of the slope of ef is 1, however the slope of df is not 1, is 1/2, so nope, they're not perpendicular lines.

step-by-step explanation:

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