In the formula, area of circle `= pi r^2`, the numerical constant of the expression `pi r^2` is________ .

If diameter of a circle is 2r cm, then area of the circle is :

If the circumference and the area of a circle are numerically equal, then diameter of the circle is (a) pi/2 (b) 2pi (c) 2 (d) 4

{:(,"Column A",,"Column B"),(18.,"If r and R be the radii of inner and outer circles, respectively, then area of a ring is _______.",(a),60),(19.,"The total surface area of a cube of edg" sqrt(10) "cm is ______." cm^(2).,(c ),pi (R^^(2)+r^(2))"sq. units"),(21.,"If the radius of the circule is 14 cm, then the area of the sector of angle." 45^(@) "is _______" cm^(2).,(d),pi(R^(2)-r^(2))"sq. units"),(,,(e ),sqrt(20)cm),(,,(f),77 cm^(2)):}

The circumference of a circle whose area is 81 pi r^2 , is

Identify the numerical cofficients of terms (other than constants) in the following expressions: 3.14 r^(2)

If the area of a circle inscribed in a square is 9 pi cm^(2) , then the area of the square is

If the area of a circle inscribed in a square is 9pi cm^(2) then the area of the square is

If the circumference and the area of a circle are numerically equal,then the diameter is equal to (pi)/(2) (b) 2backslash pi( c) 2 (d) 4