A circular wire of radius 42 cm is bent in the form of a rectangle whose sides are in the ratio 6 : 5. The smaller side of the rectangle is

Circumference of circle $=$ Perimeter of rectangle

$2\pi r=2\left(l+b\right)$

$\frac{22}{7}\times 42=6x+5x$

$22\times 6=11x$

$\therefore x=\frac{22\times 6}{11}=12$ cm

Smallest side $=5x=5\times 12=$ 60 cm