The curved surface area of a right circular cone of base radius 21 cm is 594 sq. cm. What is the slant height of the cone?

9 cm 

We know that,

Curved surface area of cone = πrl

where l = slant height

We have,

Curved surface area of a cone = 594cm² 

radius = 21 cm

Curved surface area = 594

 π × r × l = 594

= \(\frac{22}{7}\) × 21 × l = 594

= l = 9 cm