`{:(,"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)):}`

`{:(,"Column A",,"Column B"),(18.,"If r and R be the radii of inner an

1.	`{:(,"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)):}`
Answer» 18. Option (d) : `"Area of ring is "(R^(2)-r^(2))` 19. Option (a) : `"Total surface area of cube"=6("side")^(2)=` `6(sqrt(10))^(2)=60cm^(2)`. 20. Option (b) : `"Diagonal of square"=sqrt2xx"side"`= `=10sqrt2cm` 21. Option (f) : `"Area of sector"=(theta)/(360^(@))xxpir^(2)` `=(45^(@))/(360^(@))xx(22)/(7)xx14xx14` `=(1)/(8)xx(22)/(7)xx14xx14` `=11xx7=77cm^(2)`