CHAPTER 20 CYLINDER, CONES | CONCISE MATHEMATICS | SELINA SOLUTIONS | EX 20 A

 

 SOLUTIONS_PDF_LINK

 

 EX20A Q3. A cylinder of circumference 8 cm and length
 21 cm rolls without sliding for 41 seconds at
 the rate of 9 complete rounds per second.
 Find
 (i) the distance traveled by the cylinder in
   4-1/2 seconds, and
 (ii) the area covered by the cylinder in 4
   seconds.

 

 EX20A Q8. A cylindrical container with diameter of base 42 cm contains sufficient water to submerge a  rectangular solid of iron with dimensions   22 cm x 14 cm x 10.5 cm. Find the rise in the level of the water when the solid is sub-merged.


 EX20A Q14. Find the minimum length in cm and correct to
  nearest whole number of the thin metal sheet
  required to make a hollow and closed cylindrical
  box of diameter 20 cm and height 35 cm.
  Given that the width of the metal sheet is I m.
  Also, find the cost of the sheet at the rate of
   56 per m.
  Find the area of metal sheet required, if 10% of it   is wasted in cutting, overlapping, etc.

 

 

 EX20A Q10. Find the total surface area of an open pipe of
    length 50 cm, external diameter 20 cm and
    internal diameter 6 cm.

 EX20A Q11. The height and the radius of the base of a
    cylinder are in the ratio 3: 1. If its volume
    is 1029 cm^3; find its total surface area.

 EX20A Q12. The radius of a solid right circular cylinder
    increases by 20% and its height decreases by
    20%. Find the percentage change in its
    volume.


 EX20A Q15. 3080 cm^3 of water is required to fill a
  cylindrical vessel completely and 2310 cm^3 of
  water is required to fill it upto 5 cm below the  top. 

Find :
  (i) radius of the vessel.
  (ii) height of the vessel.
  (iii) wetted surface area of the vessel when it is half-filled with water.

EX20A Q18. A circular tank of diameter 2 m is dug and the  earth removed is spread uniformly all around
   the tank to form an embankment 2 m in width
  and 1.6 m in height. Find the depth of the
  circular tank.

 EX20A Q21. The sum of the height and the radius of a solid   cylinder is 35 cm and its total surface area is   cylinder is 35 cm and its total surface area is   3080 cm^2; find the volume of the cylinder.

 EX20A Q22. The total surface area of a solid cylinder is
  616 cm^2. If the ratio between its curved
  surface area and total surface area is 1:2;
  find the volume of the cylinder.

 EX20A Q23. A cylindrical vessel of height 24 cm and
  diameter 40 cm is full of water. Find the exact
  number of small cylindrical bottles, each of
  height 10 cm and diameter 8 cm, which can
  be filled with this water.

 EX20A Q24. Two solid cylinders, one with diameter 60 cm
  and height 30 cm and the other with radius 30
  cm and height 60 cm, are melted and masted
  into a third solid cylinder of height 10 cm.
  Find the diameter of the cylinder formed.

 EX20A Q25. The total surface area of a hollow cylinder,
  which is open from both the sides, is 3575
  cm^2; area of its base ring is 357.5 cm^2 and its
  height is 14 cm. Find the thickness of the
  cylinder.

 EX20A Q28. A closed cylindrical tank, made of thin iron-   sheet, has diameter = 8.4 m and height 54 m.
  How much metal sheet, to the nearest m^2, is
  used in making this tank, if 1/15 of the sheet
  actually used was wasted in making the tank ?