The diagonals of a squares is 4√2 cm. The diagonal of another square whose area is double that of the first square is

Diagonal of square = √2a [a = side]
4√2 = √2 a
a = 4 cm
Now, area of square = a² = (4²) = 16
Side of a square whose area is 2 x 16.
a₁² = 32
⇒ a₁ = √32 ⇒a₁4√2
Now, diagonal of new square = √2a
= √2x 4 √2
= 8 cm