Given:

Length of diagonal 1 (d₁) = 48cm

Length of diagonal 2 (d₂) = 20 cm

Side of rhombus = 1/2 × √(d₁² + d₂² )

= 1/2 × √(48² + 20² )

= 1/2 × √(2304 + 400)

= 1/2 × √2704

= 1/2 × 52

= 26 cm

Therefore,

Perimeter of rhombus = 4 × Side of rhombus

= 4 × 26 cm

= 104 cm