Cut the white square tile into 4 equal small triangles first by drawing two diagonal lines from opposite ends.

Area of each small triangle
= 98 cm² ÷ 4 = 24.5 cm²

Now each small triangle is right angled. The two sides that are 90° to each other are the same length since each are half the diagonals of the square.


So its area = ½ x side x side = 24.5cm²

Which means side x side = 24.5cm² x 2
= 49cm²

Now 49cm² = 7cm x 7cm
(Or √49 = 7)

So each side is 7cm long. Which means half a diagonal is 7cm long.

So length of 1 diagonal = 7cm x 2 = 14cm


Now, look at the rectangle. Notice that the length is just equal to 3 diagonals of a square.

(Look at the bottom 2 white squares' diagonals, then align them with the top right white square's diagonal.

They add up to the length of the rectangle)


So length = 14cm x 3 = 42 cm


The more difficult thing about this question is visualisation since two of the white squares aren't horizontally and vertically aligned with the rest