IKMC 2020 - Grades 11-12 - Set 2 - Self-study Question 27

Question 27

Wajda takes a square sheet of side 1 and folds two of its sides onto a diagonal as shown, obtaining a quadrilateral. What is the area of the folded quadrilateral?

Question illustration

$2-\sqrt2$
$\frac{\sqrt2}{2}$
$\sqrt2-1$
$7/10$
$3/5$