Perimeter of rectangle = 2 × (l + b)

= 2 × (6 + 4)

= 2 × 10

= 20 cm

Perimeter of square = 4 × side

= 4 × 5

= 20 cm

Perimeter of equilateral triangle = 3 × 6

= 18 cm

Perimeter of isosceles triangle = a + b + c

= 2 + 4 + 4

= 10 cm.