MHTCET

A circus tent is in the shape of a cylinder surmounted by a cone. The diameter of the cylindrical portion is 24 m and its height is 11 m. If the vertex of the cone is 16 m above the ground, find the area of the canvas used to make the tent.

Given diameter of the cylindrical part of tent, d = 24 m Radius, r = d/2 = 24/2 = 12 m Height of the cylindrical part, H = 11 m Since vertex of cone is 16 m above the ground, height of cone, h =...

read more

The colonies of recombinant bacteria appear white in contrast to blue colonies of non- recombinant bacteria because of
Option A Non-recombinant bacteria containing beta-galactosidase
Option B Insertional inactivation of alpha-galactosidase in non-recombinant bacteria
Option C Insertional inactivation of alpha-galactosidase in recombinant bacteria
Option D Inactivation of glycosidase enzyme in recombinant bacteria

The correct answer is Option C Insertional inactivation of alpha-galactosidase in recombinant bacteria. This is because - Lysozyme breaks down bacterial cell walls. Cellulase is a...

read more

A wooden article was made by scooping out a hemisphere from each end of a solid cylinder (as shown in the given figure). If the height of the cylinder is 10 cm and its base is of radius 3.5 cm, find the total surface area of the article.

Solution: Given height of the cylinder, h = 10 cm Radius of the cylinder, r = 3.5 cm Radius of the hemisphere = 3.5 cm Total surface area of the article = curved surface area of the cylinder +...

read more

A pen stand made of wood is in the shape of a cuboid with four conical depressions to hold pens. The dimensions of the cuboid are 15 cm by 10 cm by 3.5 cm. The radius of each of the depression is 0.5 cm and the depth is 1.4 cm. Find the volume of the wood in the entire stand, correct to 2 decimal places.

Solution: Dimensions of the cuboid = 15 cm× 10 cm × 3.5 cm Volume of the cuboid = 15×10×3.5 = 525 cm3 Radius of each depression, r = 0.5 cm Depth, h = 1.4 cm Volume of conical depression = (1/3)r2h...

read more

Write whether the following statements are true or false. Justify your answer :
(i) The volume of a sphere is equal to two-third of the volume of a cylinder whose height and diameter are equal to the diameter of the sphere.
(ii) The volume of the largest right circular cone that can be fitted in a cube whose edge is 2r equals the volume of a hemisphere of radius r.
(iii) A cone, a hemisphere and a cylinder stand on equal bases and have the same height. The ratio of their volumes is 1 : 2 : 3.

Solution: (i)Let the radius of sphere be r. Then height of the cylinder, h = 2r Radius of cylinder = r Volume of cylinder = r2h = ×r2×2r = 2r3 Volume of sphere = (4/3)r3 = (2/3)× 2r3 = (2/3)× Volume...

read more

The water for a factory is stored in a hemispherical tank whose internal diameter is 14 m. The tank contains 50 kilolitres of water. Water is pumped into the tank to fill to its capacity. Find the volume of water pumped into the tank.

Solution: Given internal diameter of the hemispherical tank, d = 14 m So radius, r = 14/2 = 7 m Volume of the tank = (2/3)r3 = (2/3)×(22/7)×(7)3 = 718.667 m3 = 718.67 m3 (approx) = 718.67 kilolitre...

read more

(a) If the ratio of the radii of two sphere is 3 : 7, find :
(i) the ratio of their volumes.
(ii) the ratio of their surface areas.
(b) If the ratio of the volumes of the two sphere is 125 : 64, find the ratio of their surface areas.

Solution: (i)Let the radii of two spheres be r1 and r2. Given ratio of their radii = 3:7 Volume of sphere = (4/3)r3 Ratio of the volumes = (4/3)r13/(4/3)r23 = r13/ r23 = 33/73 = 27/343 Hence the...

read more

Find what length of canvas 2 m in width is required to make a conical tent 20 m in diameter and 42 m in slant height allowing 10% for folds and the stitching. Also find the cost of the canvas at the rate of Rs 80 per metre.

Solution: Given diameter of the conical tent, d = 20 m radius, r = d/2 = 20/2 = 10 m Slant height, l = 42 m Curved surface area of the conical tent = rl = (22/7)×10×42 = 22×10×6 = 1320 m2 So the...

read more

(a) The ratio of the base radii of two right circular cones of the same height is 3 : 4. Find the ratio of their volumes.
(b) The ratio of the heights of two right circular cones is 5 : 2 and that of their base radii is 2 : 5. Find the ratio of their volumes.
(c) The height and the radius of the base of a right circular cone is half the corresponding height and radius of another bigger cone. Find: (i) the ratio of their volumes.
(ii) the ratio of their lateral surface areas.

Solution: (a) Let r1 and r2 be the radius of the given cones and h be their height. Ratio of radii, r1:r2 = 3:4 Volume of cone, V1 = (1/3)r12h Volume of cone, V2 = (1/3)r22h V1 /V1 = (1/3)r12h/...

read more

Write whether the following statements are true or false. Justify your answer.
(i) If the radius of a right circular cone is halved and its height is doubled, the volume will remain unchanged.
(ii) A cylinder and a right circular cone are having the same base radius and same height. The volume of the cylinder is three times the volume of the cone.
(iii) In a right circular cone, height, radius and slant height are always the sides of a right triangle.

Solution: (i)Volume of cone = (1/3)r2h If radius is halved and height is doubled, then volume = (1/3)(r/2)2 2h = (1/3)r2h/2 If the radius of a right circular cone is halved and its height is...

read more

A soft drink is available in two packs
(i) a tin can with a rectangular base of length 5 cm and width 4 cm, having a height of 15 cm
(ii) a plastic cylinder with circular base of diameter 7 cm and height 10 cm. Which container has greater capacity and by how much?

Solution: (i) Length of the can, l = 5 cm Width, b = 4 cm Height, h = 15 cm Volume of the can = lbh = 5×4×15 = 300 cm3 (ii) Diameter of the cylinder, d = 7 cm Radius, r = d/2 = 7/2 = 3.5 cm Height,...

read more

A lead pencil consists of a cylinder of wood with a solid cylinder of graphite filled in the interior. The diameter of the pencil is 7 mm and the diameter of the graphite is 1 mm. If the length of the pencil is 14 cm, find the volume of the wood and that of the graphite.

Solution: Given length of the pencil, h = 14 cm Diameter of the pencil = 7 mm radius, R = 7/2 mm = 7/20 cm Diameter of the graphite = 1 mm Radius of graphite, r = ½ mm = 1/20cm Volume of graphite =...

read more

(i) The sum of the radius and the height of a cylinder is 37 cm and the total surface area of the cylinder is 1628 cm2 . Find the height and the volume of the cylinder.
(ii) The total surface area of a cylinder is 352 cm2 . If its height is 10 cm, then find the diameter of the base.

Solution: (i) Let r be the radius and h be the height of the cylinder. Given the sum of radius and height of the cylinder, r+h = 37 cm Total surface area of the cylinder = 1628 cm2 2r(r+h) = 1628...

read more

The barrel of a fountain pen, cylindrical in shape, is 7 cm long and 5 mm in diameter. A full barrel of ink in the pen will be used up when writing 310 words on an average. How many words would use up a bottle of ink containing one-fifth of a litre?

Answer correct to the nearest. 100 words. Solution: Height of the barrel of a pen, h = 7 cm Diameter, d = 5mm = 0.5 cm Radius, r = d/2 = 0.5/2 = 0.25 cm Volume of the barrel of pen, V = r2h =...

read more

(i) How many cubic metres of soil must be dug out to make a well 20 metres deep and 2 metres in diameter?
(ii) If the inner curved surface of the well in part (i) above is to be plastered at the rate of Rs 50 per m2, find the cost of plastering.

Solution: (i) Given diameter of the well, d = 2 m Radius, r = d/2 = 2/2 = 1 m Depth of the well, h = 20 m Volume of the well, V = r2h = (22/7)×12×20 = 62.85 m3 Hence the amount of soil dug out to...

read more